I’ve seen many threads suggesting products but they often don’t mention FOSS projects, which should always be preferred to corporate software. With FOSS you are already boycotting capitalism, on either side. Free and Open Source ignores borders and shouldn’t be categorized in nationalist terms, no matter where some of the maintainers happen to live.
I moved my whole family since years to Delta Chat, eventually started contributing to the project and even created my own fork that is what my family is using, see: https://lemmy.ml/post/26007254
i huge recommend both SIP + XMPP software :)