If it’s a bunch of users sharing a bunch of resources from behind a bunch of different VPNs, I guess the most simple way is to tell them to expose it to the internet

Are you sharing your Linux PC with a bunch of different users? Or are you sharing your Linux server with a bunch of different users?

It’s not a factor for me, but if you continually find slow speed you could try picking a mirror that has better perf. Also dnf can be incredibly slow so you may need some additional max_parallel_downloads tuning

If you can run WireGuard on all your devices, you may wanna set up a multihop node that forward outbound traffic to the VPN tunnel via that hub

Panasonic Let’s Note, SV7 or SZ7 I think. Japanese domestic notebook for enterprises

Try Syncthing with IgnoreDelete but note that it’s unrecommended. Maybe use Syncthing as an append-only store