You can, you can run Nostream and expose it over Tor
nostr:npub1qqqqqqyz0la2jjl752yv8h7wgs3v098mh9nztd4nr6gynaef6uqqt0n47m is it possible to run a Nostr server in the way I described above?
Discussion
Tor is not really anonymous, is it?
And can I put my server working for a more famous one? Otherwise as my server is not famous enough no one will join it
If Tor is not anonymous, then nothing is. And it very well might be the latter. An onion site on Tor is as good as you'll be able to get (IMHO).
VPN is not anonymous to the VPN provider.