First - I'm not sure Sealed Sender would help against the server being changed to be actively malicious and trying to build social graphs. Second - even metadata concerns aside, a centralized system is just not resilient. Proposals like Chat Control are A LOT more easily enforceable with them than with tiny selfhosted servers.
EngineerGaming
I checked that (together with the clearnet link) a few times recently, got a nondescript error like "sorry something went wrong" every time.
TBH I feel like so many project leaders are wackos that I don't even judge the products by those, just by things they do. I still have hope in Simplex, but there were a couple of red flags, such as content scanning proposals, including clientside. Sure, it can probably be relatively easily forked to remove that specific thing, or you can choose the servers that don't do that, but it's still alarming that they try.
I prefer it because of resilience. A centralized service can be weakened, geoblocked or shut down by proposals like Chat Control. Decentralized protocols are much safer in such an environment, especially if there is variety in clients and servers.
Not necessarily. Some of them are able to use UnifiedPush so no need in a background service, and some of them (like Conversations) have background services whose battery use is negligeable.
Similarly, there's Signal-Cli. Normally, Signal only allows signups from smartphones, which is weird, because not all smartphones can run privacy-preserving OSes while pretty much anything can run Linux. This one is the only client I've seen that allows desktop signup. IDK if they broke it now, but worked a while ago.
Most of the mainstream social media is blocked where I am. Good news: a huge part of even uneducated population does indeed learn to evade censorship. Bad news: they tend use the most easily-accessible services, which are sketchy, like reselling the users' IPs as residential proxies.
They can’t force ISPs to block all of the VPN protocols in general
They very much can, I've seen it happen last year. The main protocols are VERY easily recognizable by DPI. However, there are obfuscation methods that can get through even Chinese Firewall, and they're constantly improving.
Doesn't seem to work on my phone, even thouvgh I have given it the permissions it asked...