I just tried opening it in Chromium snap and I got the "xdg-open" prompt and than a window with selection between qBittorrent and Transmission. I selected qBittorrent and it opened the magnet link.
$ snap version
snap 2.45
snapd 2.45
series 16
ubuntu 20.04
kernel 5.7.0-xanmod1
Magnet links are working.
I just tried opening it in Chromium snap and I got the "xdg-open" prompt and than a window with selection between qBittorrent and Transmission. I selected qBittorrent and it opened the magnet link.
$ snap version
snap 2.45
snapd 2.45
series 16
ubuntu 20.04
kernel 5.7.0-xanmod1