The GPLv3 license does not count network use as distribution.
You may want to re-license 2fas-server to AGPLv3 while keeping the mobile app repositories as GPLv3. This is similar to the approach taken by Bitwarden.
It should be noted that re-licensing is not and cannot be retro-active; all existing versions of 2fas-server before any re-licensing would still be under their own license (GPLv3).
The GPLv3 license does not count network use as distribution.
You may want to re-license 2fas-server to AGPLv3 while keeping the mobile app repositories as GPLv3. This is similar to the approach taken by Bitwarden.