Big +1 to collabora kernels. I've switched completely over to Collabora U-Boot + Collabora kernel compiled directly on the board via the standard "make menuconfig; make -j8 deb-pkg" command (only takes 25 minutes or so). They also have an rk3588-test branch which makes thermal sensors and cpufreq work as well. It seems to be running solidly for multiple days with no kernel panics or other weirdness. Of course there is no GPU support, I don't think HDMI out is working either. But for headless use cases, it's perfect.
There are only 2 missing pieces for my use case are PCIe3.0+NVMe support in their U-Boot, and SPI-NOR support in their Kernel DTB. I could probably steal the DTBs from either Radxa or Midstream sources, but I'll probably just wait for Collabora to do their work
