PayPal works for me. Maybe you can find a solution here: https://librewolf.net/docs/faq/ The easiest solution would probably be to use Firefox + uBlockOrigin for banking and LibreWolf for everything else. Otherwise you can find user-made "about:config" files to harden Firefox' security and privacy.
I am not tech savvy enough to give any more advice than this, but "wss://127.0.0.1:5939/" is a local address with the protocol WebSocket.
I couldn't find a solution, but here is someone who seems to have the same problem:
https://old.reddit.com/r/LibreWolf/comments/u6dyyk/websockets/