I wonder if the error does not come from Thunderbird.
When I look at my mails (in thunderbird), the links work one time out of two, or even less.
Almost systematically, the links loop on themselves and not in a browser. and this despite a good mimeapps.list.
I can always rectify the assignment of the programs in gnome, but if I stay in thunderbird, the links jump systematically.
on the other hand, links in hexchat or firefox are usually not a problem. I don't know, in fact. I need a troubleshooting but I don't know where to start. Thanks. Translated with www.DeepL.com/Translator (free version)