Generally speaking, ~19Mbit/s should be enough for a FLAC stream. But as the mathematicians like to joke “assuming, chickens are spherical and live in a vacuum” 😅😂 as others mentioned, there’s likely much more going on than only this upload so the upload / download rates might be an issue.

I would try to eliminate possible issues by isolating them as good as possible and then verifying if they are actually a problem or not.

That could mean:

• try to verify the speed between some outside device and your Netbird instance without any music streaming, buffering, … involved. For instance download the same FLAC file 10 times to your outside device, measure the rates and do this at a time where as few as possible devices / other people are active, if possible, store FLAC file somewhere on the Netbird server, to really be sure it’s not something else
• try to measure the speed between your Netbird and your Jellyfin instance as good as possible, again, ideally without any streaming involved but any kind of simple download would be best and again, best at a time with low traffic
• then possibly measure speeds between external device and Jellyfin with some downloads

If the speeds look alright you’d have to check for protocol issues, STUN problems, Wireguard issues, port forwarding limitations (?) we’d need some more details for better advice here.

And yes, I meant trying the official Netbird servers instead your local one. Same idea, basically, if everything works fine with their server, it might be some weird problem between your external device and your Netbird server for instance 🤷‍♂️

Let us know how it goes and have fun 😁