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.
we’re not classic, we’re advanced nerds engineers : signal is one church without any interoperability, so we’ve moved to both SIP and XMPP variants using differents provider in the family : everything is decentralized, exactly like email (we dont use gafam ones). It’s not that hard to enjoy xmpp, and really decentralized tools, a bit like for SIP (we have several Voip providers here).
I like SIP and XMPP, but in practice I don’t have any contacts to use it and the apps are lacking a bit compared to ArcaneChat/DeltaChat, besides the problem of losing groups because the XMPP server went down etc. there are some downsides but yes, if I was not satisfied with ArcaneChat I would use XMPP and SIP, or anything that is open source, decentralized and doesn’t require a phone number