I have two devices where I watch downloaded movies, and I don't have an issue with downloading the files on both.
But whenever I'm switching devices, I have to open the media player in the last device I watched on, open the video file to see upto where I've watched, and then go to that same timestamp on the second device.
Is there any solution to this? As in some user interface like netflix that works with offline videos but also syncs the progress across multiple devices?
jellyfin is the way to go, you need to keep host machine up though
try it first, and if it pleases you, then invest into a mini PC or a old abandon PC or even just a raspberry pi to host your media from there
Jellyfin does most of what you need, but if your device gets offline it has no way to send the current playback position to the server, which in turn has nothing to sync.
Use Jellyfin
hdobox I think
not available for offline. You can stream in stremio though. it syncs through devices
Plex, jellyfin, emby are the main ones everyone uses