Looks like it's not fully functional yet. This was one of the most difficult parts dealing with Linux phones.

https://mecha.so/blog/mega-mecha-march-2026-update#lte-testing-on-going

as far as the speakerphone thing, I'm fine either using Bluetooth or the 3.5 mm headphone jack. But that's just me. It would be a hassle having to out something just to pick up a call but hopefully someone has a better solution like the one you suggested.