These platforms as of now do get support from nVidia - but in form of upstreaming (to linux kernel etc.). Actually you can run Ubuntu 20.04 with v4.9.x kernel with the BSP from latest Jetpack 4.6 (but need to adjust config / and hack a few things) - currently running this w/o issues.
Ubuntu 22.04 will need upstream kernel at this point. Upstream kernel (5.15+) does get an open-source GPU driver (host1x) but I haven’t tested that yet.
If you’re not familiar with Linux kernel internals, check out armbian (runs on nano with upstream kernel).