Jellyfin local IP detection with Cloudflare

[TheDreadPirate]

I'm using pihole, and the idea was to put an A (or CNAME) record in the DNS settings. It's enough?

That might work.  Give it a try.  Worst that can happen is that you have to revert.

To add to this, using Cloudflare tunnels for a purpose like Jellyfin is against the Cloudflare TOS supposedly.

I have read various information on this point, and I have removed some features that should be problematic, such as page caching.
Are you referring to this? Or are you referring to the use of jellyfin as a type of service?

Video streaming through a cloudflare tunnel on a non-streaming tier is against their TOS.  It is rarely enforced, but we don't recommend risking it especially if you also have your domain registered with cloudflare.