Signal is using Google Push messaging, but it could be used with websocket. And officially it’s not on fdroid because they don’t want forks of their app
Xiaomi devices are a bit annoying to unlock but you should use the official way. I’ve got a xiaomi device and unlocked it. So first you need to be patient maybe it’s not going to work for the first time so try to unlock it and if it doesn’t work just wait a couple of weeks… And you should maybe ask a friend or family member to take their Sim card only to log into a xiaomi account and allow OEM unlocking. You could try an other method but when there is an official way (annoying but official) you should use it, safest and “easiest” way.
You’re mid right, the when something AI based is announced this is really criticized by some people and there are almost right. When something new pops, like windows recall, it is certain that this “new” feature is really not what AI is capable, and asks really important questions about privacy. But you’re right on the fact that Linux should be a bit more interested on AI and tried to made it the right way! But for now there’s no really good use cases of AI inside a distro. LLMs are good but do not need to be linked to user activities. Image generators are great but do not need to be linked to user activities… As exemple when Windows tried Recall and failed. Apple iOS 18 wants to implement that, and this should be surely a success inside the Apple minded people. But here where FOSS, privacy and anti Big-Techs guys are the main people that’s absolutely sure that every for-profit “new AI” feature would be really hated. I’m not against this mind just giving facts