Secure isn’t a binary. Depending on your threat model, using Plex is impossible to use securely!

It’s definitely easy, and the secure part is debatable.

I have a jellyfin server set up that you access like this:

https://my.servername/jellyfin

Username and password is all you need aside from that. Apps for most platforms or access in a web browser.

I’ve got a bunch of friends accessing my jellyfin server. It has clients for most devices now.