matemo the patch (its opensource) for Shizuku
Could you share the patch repository's url?
matemo Have you ever thought that Google artificially allows these features such as VoLTE/VoWIFI for only "supported" countries? I believe that this is true because the Pixel devices themselves support these features, but the firmware restricts them for users from "unsupported" countries.
I don't believe Google is blocking things via the firmware. If it works with the patch you've mentioned, it's solely an OS thing. But it wouldn't surprise me if Google added support for certain markets and neglecting others for selfish business reasons. In fact, I'd bet on it.
matemo What exactly is so hard about it?
As just a regular community member, I cannot speak for the GrapheneOS dev team, but I don't think the issue is that adding support for other carriers is "hard." The issue is a dev might not be anywhere close to the country to add support or test if configs are working, then if they did add support, then what about people using other carriers in other unsupported countries? They might expect support to be added for them as well.
Or directly modifying the system to include stuff the patch you've used in the past might also be a bad idea. Upstream changes to AOSP might break something and once again it would be difficult for the devs to troubleshoot and fix this kind of issue.
Once they add support for something, then they're kind of on the hook for continuing to support it. If something breaks and they're not aware of it because of the location of the devs, then people start to complain about "bugs," which is obviously a bad look for an OS focused on both privacy and security. "Bugs" make the project sound like the team is incompetent. In my experience as someone who has been active in the community, many people blame the project for issues caused by upstream changes. For example, the project cannot fix firmware issues. Only Google can, but for most people it's hard to know which team exactly is responsible for something breaking, so they default to blaming GrapheneOS.
The project does its best to make sure all releases are stable. Each feature that's added can be broken by upstream changes, and fixing stuff takes time, delaying updates. Obviously that is a bad thing since GrapheneOS does its best to ship all upstream security patches ASAP.