Risky

On Android and IOS, i like Snikket.

On desktop, Gajim

I usually name mine after songs that I happen to be listening to at the moment.

Ranger, mostly for bulk renaming

I use it for seeing/replying to texts on my desktop. It works great for that with xfce.

I would get a powered USB hub for your hard drive, then plug in the hub into your RPI4. The usb ports on the pi cannot handle a lot of power(from what I remember).

Jellyfin, I’ve run mine for a couple years now(ever since the pi4 came out) and it’s been great. The only thing to consider is turning off video transcoding, its not able to to transcode anything HD or over. Other than that, its great. I use it for videos and music.