I just found this cool utility a couple days ago and have found that it’s a great solution to sandboxed versions of Discord being unable to provide rich presence. It’s a Python script that queries the Steam web API to get info to forward to Discord’s API. The “installer” sets up a systemd service that will auto-run the script for you.
It requires you to get your own Steam API key which was a trivial, though slightly buggy, process for me. You can optionally use your own Discord app ID, or just use the one owned by the guy that created this script.
It doesn’t make use of the games original Discord RPC integrations, and their more-in-depth game details that it can bring. See https://github.com/ValveSoftware/Proton/wiki/Enabling-Discord-Rich-Presence or https://github.com/EnderIce2/rpc-bridge for ways to fix it.