at least java minecraft does that part right with the offline mode that switches off auth checks. for a real online server you need a login plugin then (makes sense that some form of username ownership verify is needed in that case) but for a secured LAN it is usable by default.
same. saved my ass already a few times when doing some reverseengineering voodoo. being able to set a valid https cert makes it easier to redirect apps than to bypass forced HTTPS. had to pretend to be a update server for something once and patching the URL was enough via getting a cert quickly (using DNS-01 challenge, no exposed ports ever)
Good thing is that the content is not lost for those that know to surf the web. But those locations don't help reddit at all (main one is the wayback machine from archive.org and then there is a raw datadump of anyhting up to march 2023 as JSON)
you can use a secondary firefox profile. starting firefox with the --no-remote -p
switches allows to load it alongside the main profile (-p loads the profile manager and --no-remote suppresses the "open new window in existing profile" behavior