Ever since Mv3 came into enforcement I've been using a local DNS blocklist in /etc/hosts (UHB more specifically) for locking the browser down as much as possible. Unfortunately this has lead to some major issues when browsing, i.e. 5-10 second latency for every single request that goes through the browser. Can't completely stop using some Chromium-browser since I need to test my work on the browser at some point.

I'm suspecting it's due to the browser waiting for some telemetry endpoint, or trying to get around the block through some other means (which won't work since outgoing DNS via anything else but the gateway is blocked in the firewall), and giving up after a specified time. At this point I've narrowed the issue down to the full version of UHB, as when toggling this off the requests no longer hang before going through. Firefox doesn't suffer from the same issues – every Chromium-derived platform suffers, though, including Electron applications like VSCode. Toggling async DNS off hasn't helped (which previously supposedly has helped some), neither has turning secure DNS (read Google's system DNS sinkhole workaround) off.

Out of curiosity, has anyone else encountered the same issue or is using a version of Chromium that's not suffering from the same issues? This is getting a bit infuriating, and though I've already moved my browsing on Firefox, it's still bothersome to run e.g. UI tests when every fetch operation takes 10 s. This even happens when connecting to stuff running on localhost or LAN addresses.