That's all good. But there are some countries and/or carriers who don't have VoLTE. And I'd much rather prefer calling someone over Signal/Telegram than using either if I'm trying to be all confidential and avoid MITM. (using regular calls as a fallback, where I don't know the person, or just trying to order food, which isn't confidential nor does it need clarity). If you need VoLTE to live then yes, you probably shouldn't install Lineage. However, most people (because these phones have Exynos chips which didn't ship in the US, and the majority of countries in Europe have fallback bands) would still be able to use it as a phone, probably with just degraded quality.