Wonderful machines

"Alle Rechner funktionieren und können ausprobiert werden."

https://invidious.snopyta.org/watch?v=V3xGl9vwIMc

All exhibition items (computers) work and can be tried out in practice.

If you're interested in older systems like this you may also be interested in for example the PDP-6 and PDP-10. There are people actively working on such things both real and emulated in #pdp-10 on irc.freenode.net. The most active discussion seems to revolve around the Incompatible Timesharing System, which RMS hacked on while working at MIT in the days before the GNU Project.

https://en.wikipedia.org/wiki/Incompatible_Timesharing_System