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.
It’s hard to say. “Open core” means that most of the software is open source (licenses vary) but some features are locked behind a paywall. Gitlab takes this approach for example, also maybe onlyoffice.