Fedora might be a good option, but it might require more setup with an Nvidea GPU. They use Wayland now, are a Gnome based distro, support full disk encryption. For me the package mangar has been fine, and they do support flatpak. It is a very large distro with backing from RedHat. So it should generally be stable.
Pop_OS! Seems to be the great distro if you just want to game and watch videos without any issues arround setting up the drivers. It has been a quite stable distro for me and it is quite similar to Ubuntu. Unfortunately this distro doesn’t have Wayland yet.
Manjaro is an Arch based distro, but it had some issues with using packages from the AUR. They do run Gnome on Wayland by default.
It would be nice if Jagex would confirm that it is fine to use this laucher. As far as I know we have no more information than this tweet from Mod Ash: https://x.com/kaelygon/status/1763667578315042847 Bolt does work the same as the official launcher, so it should not be a problem…