[deleted]
The best option is not to rely on centralized solutions. Keep in mind that Signal has not update server code for months without explanation. BTW, you have no idea what it is implemented on server side.
You can consider using your own XMPP server in i2p or Tor network. It's easy and cheap. If someone has money for Pixel they should have 'pennies' for Pine board or RPI or something similar.
https://discuss.grapheneos.org/d/2216-grapheneos-without-sim-signal-alternative/25