In the recent few releases, GrapheneOS has added support for enabling VoLTE and VoWiFi where carriers don’t allow to use those services. I copied changelog from official website related to these settings below:
• add support for force enabling VoLTE, VoNR and 5G for carriers where those aren't supported with the standard configurations
• Settings: add support for forcing VoWiFi availability
• Settings: improve the carrier configuration override by improving the summaries, adding detailed descriptions and using clarifying the options force features to be available since there are also toggles for directly enabling/disabling the features in the main SIM settings screen
discuss.grapheneos.org/d/27029-grapheneos-version-2025100300-released/32
In the above thread, GrapheneOS has commented that if there are other things people want to be able to override and they can justify the use case, we can consider adding those too.
Can I please request the feature of adding Wi-Fi calling from SIM 1 over cellular data of SIM 2 in a dual SIM configuration?
Whenever I travel overseas, I have to rely on Wi-Fi connection to use VoWiFi on my primary SIM. But to remain connected to Wi-Fi all the time while traveling is very difficult. This can be solved by getting a local SIM 2 and then using VoWiFi from primary SIM 1 through the cellular data of local SIM 2. In this configuration, Wi-Fi toggle can be completely turned off. This functionality is available in iOS and probably it was available in earlier AOSP versions by the name of backup calling. It does currently work on Pixel and Samsung devices, but all depends on the carrier and in my limited testing most of the time they don’t enable this feature, whereas in iOS it always works.
Similar to force enabling VoLTE and VoWiFi in the recent GrapheneOS releases, if this setting can also be force enabled then that would be extremely helpful.