If you can afford it, I think the Librem 5 is the best linux-first phone at the moment. Both it and the PinePhone Pro are roughly as fast as each other, but the Librem 5 has a much more premium feel, and the hardware kill switches are much more accessible, if you're into that kind of thing.
Back in the day, when the Librem 5 was $1000+, it was a no-brainer for the PinePhone Pro, but I feel it is much more reasonable to recommend the Librem 5 now.
You can make it work as a daily driver, but I wouldn't want to depend on it for life and death situations. Calling generally doesn't work very well - either one side can't hear the other, or the audio quality is too quiet, or not very good. It's probably possible to fix if you know what you're doing, but I don't know what I'm doing :)
I carry around a dumbphone and a SIM removal tool, so that I can call someone if I really need to. If you're happy to do that, I feel it gives you the best of both worlds.
Otherwise, one alternative is to be an Android-first device, that has good support in PostmarketOS, e.g. the Oneplus 6/6T. Mobile Linux has had such an impact on these devices that the price of these on eBay has gone up in some areas over time :D
Good luck!
One thing to be aware of is that riding around a lot with the phone attached can cause the stabilisation sensor in the camera to go wrong. When this happens your camera feed starts wobbling around all the time. This happened to a friend of mine and let's just say his snapchat stories had a very distinctive look :)
I'm not sure whether more expensive mounts do a better job with this (I think his was quite cheap) but make sure to do your research if you're planning on using it a lot, and you care about your phone's camera.