> where a mainline kernel will work

For some definition of a "mainline kernel." My preferred Linux distro is Debian, I still can't run a Pi 5 on Debian over a year following release. (I don't know if this is for lack of Pi engineers not pushing stuff upstream or Debian/kernel devs not being receptive to PRs, but I suppose the answer is somewhere in between.)

I do run Debian on Pi 4B/CM4 and others. At present I'm working on getting 1-wire with a DS18B20 working on a Pi Zero W and it has not been easy, but that might be me.

I was truly excited to see the CM4 released because it provided a PCIe slot and which can support a proper storage interface on a Pi. I don't see a compelling feature on the CM5 so I'm not going to jump on one just yet. I'll probably get one at some point.

I do agree that the Raspberry Pi community provides reasonable support. I have, however, found the Reddit community occasionally toxic and have had questions on the official Pi forum removed w/out explanation. (I asked why the Imager did not offer the most recent OS releases in the menu, requiring that I manually download them.)

> For some definition of a "mainline kernel."

...but I bet you can port Raspberry's patches to a vanilla kernel tree relatively easily. Good luck with it with other providers.

I used OrangePi and Radxa. Radxa rock was a huge disappointment in that regard.