SDF has put a PDP-10 running TOPS-20 online. I've already tried it and as a *NIX/BSD fan, I enjoyed tinkering around on it.
If you want to try it, ssh firstname.lastname@example.org
and 'login new new'.
More info at https://tinyurl.com/2746p56z
--- GoldED+/BSD 1.1.5-b20220504
* Origin: Outpost BBS * Johnson City, TN (1:18/200)