Gregory's Server
… for regular users. The former is very similar: capsule@.service can be instantiated many times, and each will spawn a per-user service manager too – but has DynamicUser=1 set, i.e. it's a service manager for a dynamic, short-lived user.
So, what is this good for? The idea is that you place some service definition files in the .config/systemd/user/ subdir of /var/lib/capsules/<somename>/. The latter becomes the $HOME of the dynamic user created for capsule@.service.
With that in place, …
… you can then do "systemctl start capsule@<somename>.service" to start the capsule. This spawns a per-user service manager, with a shortlived dynamic user. Once you do "systemctl stop capsule@<somename>.service" it goes away again. And inside that service manager all services defined and enabled in the aforementioned directory will be invoked.
You don't really have to place service files in that dir btw. You can also just start the capsule as-is, and then invoke stuff dynamically inside…