Ah, yet another repo. I’m just looking for kernel source as I’m cross-compiling Gentoo onto it. So if I get what you’re saying, I can use the “shipping tags” link you gave? I definitely want a LTS release and 6.18.x is that, but it’s arm64. Will the 6.18.21-arm64-k3-r29 tag work for BBB Rev. C?
Yes, to my mind the BBB, and arm in general, is just mainline linux. There is basic support for most of the AM335x hardware. The one area that isn’t mainline is the graphics, TI did do some kind of realise of the graphics, but it was never mainlined. Looks like someone started doing a mainline driver - but that project has been stalled for several years. So if you need the graphics to work then you’ll be stuck with old kernel versions. Otherwise it’s as @RobertCNelson said, there have been various spinning of the default kernel spun for the BBB. So just grab whichever version you need is easiest. Compelling the kernel from scratch can be done on a BBB, if you’ve installed the development environment (so GCC and the like). It’s takes several days to compile, and if you want a compressed kernel you need to limit the memory usage, as the BBB has limited memory. My guess is most people that compile the kernel do it on more capable machines that support the armv7 compilation tools.