Network effect is the biggest problem for messaging services, and so I would still push for Signal over the alternatives that are technically better. This guide seems like it is focussed on users who are new to the space

I agree with the Linux recommendation, but I'd offer CachyOS over pure Arch for newcomers. The limine bootloader gives a lot of peace of mind, since you can tell the user "if you get a bad update, reboot and pick an older option on the first screen".