Firefox, Chrome, Edge, will all warn you about self-signed certs or cert mismatches but allow you to continue. You’re completely correct that SSL/TLS needs a certificate, but it doesn’t need to be CA issued or in any way legitimate for the encrypted tunnel to be established

You don’t really ‘need to’ in a world where a good proportion of people will happily click ‘continue anyway’ when they get any sort of certificate error

Valid, but if you get a dedicated one, you could put in a SIM from a different network that has better coverage, if one exists

A cellular signal isn’t one single thing. A GSM booster will improve the availability of a GSM signal, but that’s calls and SMS but isn’t going to do a lot to provide mobile data given that 3G coverage is basically dead and 4/5G data doesn’t operate on a frequency that the GSM booster will be doing anything for. You can get cellular WiFi hotspots that you put a SIM in and they basically become your WiFi router or just use a cellphone that has hotspot functionality

Unpopular opinion but defederating Meta is a terrible idea. What are people thinking will happen? Allow them to federate and you’ll have mastodon users able to view and interact with posts from Threads without needing to be concerned about ads or tracking, without giving over any more control of privacy than they would to any other fediverse instance, and without needing to possess accounts homed within the Meta infrastructure.

Defederate them, and anyone who wants to interact with anyone on threads will most likely need to maintain a presence on both and handover more personal data to Meta than they otherwise would.

Defederating is actively hostile to fediverse users.

I have a chrome plugin to strip any Pinterest results from searches, it’s the absolute worst