These URIs are the references to technical documentation in Google Android site - they are used in error messages by various libraries.

The presence of the URI in code does not mean that the app communicates with this URI.

On the opposite, the absence of the URI in code does not prove that the app does not communicate with any given URI - the URIs can be obfuscated in many ways.

So this scanning technique to discover potential attacks is completely inefficient, and it creates unnecessary work of removing URIs from code, but achieves absolutely nothing to prevent the actual network connection - any malicious app can hide them and make them invisible to the scanning.

Another example would be simplex.chat domain. While the app contains it in code, the app never communicates with this domain, and it is only used to namespace the links and to allow showing QR code for people who don't have the app.

You cannot establish what URIs any given app communicates with by scanning its code - you need to proxy all traffic and monitor all connections that the app makes.

just delete them after a set time - preset servers have it at 21 day

You don't have to encrypt the message, simply observing it won't compromise security. You only need to ensure that the channel is 1) authenticated (that is, you know who you send to) 2) cannot MITM you (that is, replace the link). MITM can be mitigated with security code verification via yet another channel, but SimpleX relays cannot MITM key exchange (unlike any centralised service).

Your CLI fails to connect to the relays, something is not working. Are you connected to the internet? Possibly, you cannot access the relay.

Try:

ping smp4.simplex.im

telnet smp4.simplex.im 5223

If you can't connect to preset relays, you need to either use VPN or some other relays (e.g., self-host).

yes, occasionally :)