@Edent Great post, if only our telephones could be the general purpose computers they were born to be!
In practice, I think you've hit the nail on the head with the protocol and security issues. You can 100% self host on a #Pinephone. Just not on anything that will run your banking apps.
There's a need for a new protocol approach that includes buffering if you want to cover the downtime/out of signal or battery case. One neat partial solution would be failover #DNS to a self hosted backup.