SOLVED: Can't see other clients in the "cast to" devices list

[auxym]

Which reverse proxy do you use?  Caddy automatically supports web sockets.

I use Cosmos Server, and that's it. If I understand correctly, it has its' own reverse proxy built in, which probably contributes to my lack of understanding of what a reverse proxy does as I haven't used a server without a reverse proxy to know the difference.

Additional update:

I've now discovered that only Administrator accounts are able to remote control other devices or receive playback status from other devices, which seems to be why "Remote control" doesn't seem to work properly.

Not the end of the world, but I'd prefer to be able to log in via a less potentially destructive account on devices. Does also seem to defeat the purpose of non-admin user accounts. My main use of Jellyfin is to remote control a Windows Surface tablet for music on one of my sound systems. That tablet is accessible to anyone in the house, so having it logged into an Admin account isn't ideal.

In the settings for a user, there are two options for "Allow remote control of shared devices" and "Allow remote control of other users", that might be what you're looking for.