Couldn't find the answer online and spent unnecessary hours trying to solve it, so I'll plop the answer here.

Problem

Software like SDR++ can't find any devices
systemctl status sdrplay shows following errors/warnings:

[3943]: sdrplay_apiService: UpdateDevicesL: ERROR: libusb_claim_interface() -6
[3943]: sdrplay_apiService: sdrplay_apiServiceWorkerThread: ERROR: UpdateDevices() failed 1
libusb: warning [libusb_exit] device 1.5 still referenced
libusb: warning [libusb_exit] device 1.1 still referenced
libusb: warning [libusb_exit] application left some devices open

Based on what I found, -6 corresponds to LIBUSB_ERROR_BUSY. The device has been claimed by something else.

Specific problem

I found this blog post on using RSP1 clone without the proprietary software: https://blog.marxy.org/2023/05/using-sdrplay-rsp1-clone-with-cubicsdr.html
It mentions blocklisting some kernel modules which capture the device.
Comparing lsmod | grep msi with known good system (Arch Linux), sure enough, these aren't loaded while in Linux Mint they are:

msi001                 20480  1
msi2500                36864  0
videobuf2_vmalloc      20480  1 msi2500
videobuf2_v4l2         36864  1 msi2500
videodev              352256  3 videobuf2_v4l2,msi001,msi2500
videobuf2_common       81920  4 videobuf2_vmalloc,videobuf2_v4l2,msi2500,videobuf2_memops

Solution

Add the following lines to /etc/modprobe.d/blacklist.conf to blacklist these kernel modules:

blacklist msi001
blacklist msi2500

And reboot.

Personal note/rant

I spent so much time... I tried different API versions, so I also had to uninstall the newer ones which with this stupid software can only be done with careful manual removal of files.
I tried different USB ports (just in case), reinstalling SDR++, SoapySDR, installing some other potentially interesting looking libusb related packages, trying to find at least one other person with this issue...

And in the end it's just interfering kernel modules like with RTL-SDR.
Well, if this gets indexed the solution should be easy to find based on the error now.

Image source: https://www.telepolis.pl/tech/sprzet/ulefone-armor-34-pro-armor-33-pro-armor-mini-4-mwc-2025

Just another ridiculous device from Ulefone.
Unfortunately, I can only find its dimensions, but not weight. The thickness is whopping 3.4 cm (1.34 inch).

Currently I own a smaller one, Armor 24, which is still 2.75 cm (1.08 inch), but even that weights 647g (1.43 lbs).

I wonder if these brands like Ulefone, Doogee, Unihertz will reach the 1kg mark at some point.

Be ready to dial 911 if it falls on your face.

Edit: Found answer here: https://groups.google.com/g/tigervnc-users/c/c4mihwmz_bI
Apparently only local sessions have access to certain HW. Audio devices are also in group audio, so I added my main user to that. Might be the fix for other stuff if I figure out the exact issues.

So I have a Mini PC running Linux Mint (headless) that I want to (sometimes) access over VNC remotely.

Using just TigerVNC has issues. First, XFCE got reset to its defaults. I don't mind this too much. There are some password prompts and all power options other than "Log Out" are inaccessible (DBus seems to be running if that's related. But also, more just annoying than an issue.)

The biggest problem is with audio. There appear to be no audio devices with aplay -l when run as regular user, but they do show up for root.
I tried running a session as root, but...
User
Root
I don't even get the Dummy Output.
It seems to have a problem with connecting to PipeWire (maybe because root can't use DBus? (just a guess, remembering errors of some apps when run as root))

So that's what happens before logging in with LightDM.

If I do login in GUI, things will magically work

(The Mint customization stays broken after it happens once)

So I am guessing some more stuff is started when using LightDM, and I'd like to know what exactly it is, to reproduce it.

As for why not keep using autologin:

1. I don't want a GUI session running when unnecessary
2. x11vnc is somehow extremely slow compared to tigervnc even with same compression, quality and resolution

Thanks.

https://en.wikipedia.org/w/index.php?oldid=1274673353

I've always had it on, but it's kind of a pain in the ass. Especially on worse (not necessarily slower) networks.

On laptop it's fine for the most part since the use-case is a bit different, but on a phone it's causing me some annoyances/issues.

With my carrier indoors it takes on average 62 seconds to connect. This is pretty annoying if toggling/switching VPN servers more often.
But when travelling (e.g.: in a train) it can make the difference from slightly spotty signal to almost never being connected successfully, impacting usability.

As such, I often find myself not even using VPN in such cases in the first place.
For comparison, plain Wireguard is done before I can pull away my finger from the "connect" button, usually even on 2G EDGE.

Do you keep this (perhaps a bit paranoid-level) option on?
Even if actually useful in the future, it would only protect traffic recorded from User to VPN anyway.

TL;DR: My particular 5.25" drive started spinning probably a bit too fast when used externally on cheap USB + 12V to SATA adapter.

So I got a 5.25" drive from an old PC that I wanted to use as external with USB SATA adapter. I mean, I have a slim portable one, but 5.25" is cooler, you know.

It seems the controller, laser and tray motor are powered from 5V rail while spindle and laser assembly motors are powered from 12V rail.

In my case, 5V source was USB on laptop and 12V an external power supply with the cheap SATA adapter.

Reading worked, so I tried burning a DVD+RW. Brand new undamaged disc. Unfortunately, it seems the higher power required caused too much voltage drop and it kept failing. The drive states 5V@2A and [email protected] max. USB tester looked fine on source side, so probably the cheap SATA adapter's resistance was to blame.

Clearly, looking at the burned area, there wasn't enough power (or something else failed):
Stripes

Well, the failure was interesting. A few times it just stopped communicating and I had to unplug and plug it back in.
But the other one was that it would just spin up from 4x to god knows what high speed until K3b shown I/O error and ejected the disc after a couple seconds.

Last time I tried playing with it. When it started speeding up, I started toggling the 12V power supply. No I/O error, and K3b shown "0.8x", but I got bored of it and it probably wouldn't write anything readable anyway.
So, I turned the 12V back on and let it go full throttle. I/O error, and split second after it started spinning down a faint crack sound. And there we go, the disc started cracking, it would probably shatter soon after.

I also tried burning a Memorex DVD+R at 16x. I put front of the drive into a plastic bag to contain potential shrapnel, and started burning. Nothing interesting. I set it to 16x, it kept bouncing between 5 to 7x and produced nothing readable (just stripes again).

It says post anything, right?

So yeah, 3AM it was and what would I be doing, sleeping? Nah. Oof, I wake up in 2 hours...

Nevermind that, here's per color test page:

I filled the CMY cartridge with blue FP ink. All three colors.

But first I flushed it with tap water. I just filled it with water and sucked it out repeatedly. I did not get all out, but enough. Then I shot in around 3ml of FP ink that I sucked out, and put in like 6ml of it in and sucked out 1ml to get it flowing.

The cartridge was partially dry for like a year. I thought all the nozzles would be burnt out by now.

Basically I did all that shouldn't be done.

And here's a test the other way around:

Nice black, but with a lot of bleed-through:

Top text: Oh good, you're finally awake
Bottom text: Humans? Fursuits? What are u talking about? Lets cuddle
Description: (Text background) Drawing of a furry - dobermann named Copain (she). Anthro, longer dark hair, orange to brown fur, cyan eyes, black colar with buckle around neck, black short-sleeved shirt. Hands off-screen towards viewer, smiling with open mouth with toungue (inside mouth) and upper teeth visible, blushing, ears perked up - outside darker brown, inside lighter orange-brown. 5 pink hearts drawn around the character.

If the description is badly written, blame me. I wrote it.

Sources

Lower resolution:

https://bsky.app/profile/helicopterfood.bsky.social/post/3lihmwjesrs2f
https://www.deviantart.com/kurutyan/art/wake-up-1161156897

Higher resolution:

https://sfw.furaffinity.net/view/59929967/
https://e926.net/posts/5384868

Disclaimer: There may be NSFW (18+) content on these sites

So, after end of shift, which was too early for being a minimum wage hourly paid job (3 hours, bruh) I spoke with a coworker.
I basically said I rather take my time, since working longer means more money, and that I even take the time to double or triple check the counts of things since I prefer to do it accurately rather than fast.

After saying something along the lines of "If I don't get a negative point for low speed, it's probably good enough." I heard a familiar voice:
"Come look at your speed -"

Aaaaæäãæâåæuuæaâä, my throat tightened, my eyes looking for source of the voice somewhere on my left. They find a gap between boxes, just large enough to see the eyes of flaming doom. My doom.
My legs, almost on their own, start making coordinated movements that move the upper part of my body around the boxes towards my boss who's staring at a laptop screen, all while my brain resonates "I done fucked up".
My body now standing at the destination, few steps away from where I was, but still a mile road away. My mind clears enough to ask the eyes for what they see. They see a glowing rectangle, a laptop screen, thousands of squares from far away forming an image of a spreadsheet. One line a different shade, higlighted, it bears my name.
Far below average, in fact the slowest.
Boss standing on my right dooms me with final verdict, "That is slow enough for a negative point."
Indeed, one third the average speed today. Worker x 0.3, one third.

I was just told I don't need to count everything twice (or thrice which I haven't mentioned but sometimes do as I distrust myself), and that small mistakes in accuracy are tolerated.
And also that she noticed me being below the average quite often. I wish I had access to those statistics.

Damn.

Why waste time by sleeping, right?

Ignore "REM", Mi band 4 doesn't measure that.