Librewolf has some trouble with some websites. For example, it won’t load one of my own that makes a GRPC request over TLS, stating that the certificate issuer is unknown despite it being the same certificate used on the accepted-as-secure page the request is made from.

I’m trying zen-browser.app now. It’s also an open source fork of Firefox. The UI is much changed: vertical tabs and workspaces. It was a bit of a shock, but it’s growing on me.