Has the app been tested to work with GrapheneOS (without requiring Google Play Services). This question applies to both the esim function and/or the relay feature.
Is no panacea to this problem everything has it's limits. Pairing an IMEI+IMSI rotation (which is perfectly lawful in many countries, grey in some and criminally prohibited in only a few) can be a very effective defense against network level threats to privacy.
The IMSI change is only truly effective if paired with an IMEI rotation - which as others have noted is legal (usa). So now we have a service provider that supports IMSI rotation I guess it is up to folks who can work on the hardware level to add support for IMEI rotation. I heard that GrapheneOS is developing its own hardware. It's possible we may have a very effective defense against cellular layer privacy attacks in the near future.