I've installed it lots of times (maybe 15 or 20 on maybe 10 graphene phones, and it's Signal so sometimes things just don't work, or sometimes they don't work for a while and then later do work, so just asking if anyone knows right now. I logged into Signal on one GrapheneOS phone yesterday. But then tried to install it on another GrapheneOS yesterday (different phone), because someone in my family couldn't get Signal to install on their (GrapheneOS) so I was trying to make a video to show them how. Didn't install last night or today. I should say, create an account, not install. It seems to install fine, but can't get past the Text Code screen of the account creation.

It gets as far as the Verification Code (where it wants to text a code). We click OK, but it just says 'Error connecting to service' and sometimes another message also saying it can't connect to the service. (The phones have wifi, installed Signal from Aurora, everything seems to work fine). I also gave Signal app the phone number of a GoogleAndroid phone to try to send the Code to that but same error message.

9 days later

I had the same issue because I tried going activating it without having a SIM card in(eSIM) in this case. I had the same error after installing the eSIM but then I cleared the cache for the app and it worked, hope this helps someone!