So I've been trying to experiment with it, and I'm pretty confident what's happening here is a result of you using the snap version of Joplin; officially it's unsupported. You could run snap list to see if that's the case.
The snap uses a different backend for opening links than the normal release, and this is causing issues. I'm trying to work out exactly what issues, because I'm noticing some unusual behaviour differences (E.G, when Zotero is installed from the community packaged Deb file, it actually does work fine, weirdly...). It'd take a couple of hours to sus it out, if it's even fixable.
In the interests of getting you up and running as quickly as possible, I'd suggest transfering your Joplin data over to the AppImage version. There's some Linux installation instructions here.
You can go on the help menu and click "open file directory" to get the folder where all your snap stored notes are. Copy this over into ~/.config/joplin-desktop, and the AppImage version would import everything just fine. At that point I'd then just run sudo snap remove joplin-desktop so there's only the one version installed.
Everything works fine on the AppImage release in my testing.