Nanos are only supported through the 4.x series of JetPack/SDK Manager. Note that L4T is what is flashed, which in turn is just Ubuntu plus NVIDIA drivers. Here is a URL for L4T releases, which in turn goes to a URL which also includes the specific JetPack/SDKM release (one L4T release is tied to a JetPack/SDKM release):
https://developer.nvidia.com/linux-tegra
Sorry, Nano is in a maintenance phase and won’t get new features. This is why you won’t see it with the newer R34.x/R35.x+ L4T (JetPack5.x+ is not supported for Nano).
Xavier products and newer support R35.x+ L4T (JetPack5.x+). I think Xavier just announced that in 2023 it will also go to maintenance, which would that if you want new features you would be better off with Orin.