Can’t help much since I haven’t tried running a Matrix server in a while now, but are you using Conduit or Conduwuit?
Conduwuit is in much more active development and has more features implemented and bugs fixed.
You could also try opening an issue on Github / ask them on Matrix.

Exanima is basically the prequel to the main game they are also currently working on (Sui Generis).
It’s also planned to have multiplayer after the story part is finished.

Check out Exanima.
There’s a nice video of theirs showcasing some complex object collisions - https://www.youtube.com/watch?v=R9-ihvHJdJE
And some neat cloth physics at about 14:25

I believe that’s more of a goal for Sui Generis. Which is the game they initially begun working on (and still are).
They do have some dialogue with Derrin that gives us some lore, so I’m guessing we’ll get more of that.

I also had Exanima in mind.
The story is actually already there, it’s just easy to miss :)
Although I’m guessing once they finish up work on the AI, roles and dialogue system soon, there’ll be more of it.

Dendrite doesn’t support sliding sync afaik https://github.com/element-hq/dendrite/issues/3236

Other than Synapse, I know Conduwuit has sliding sync support.

Neat! Glad to hear
Yeah they’ve done a good job with their documentation.
I was tempted by it several times already to try some features I didn’t even consider using.

Yup.
Tailscale has some documentation about it, and also a bunch of examples (And apparently one specific to Immich).

Since you already got some replies, a bit of a different approach would be to set those services up using Docker and having Tailscale as a sidecar to each one of those.
You will then be able to access each one as a seperate device. immich.*.ts.net etc.