I use [https://syncthing.net/](Syncthing) because it's serverless, works on various Linuxes and Android, pretty easy to set up, and I trust it.
I trust it because I can get it from 3rd-party repos — Debian, Fedora, F-Droid — and I trust that they wouldn't all allow malicious software that claims all communication is encrypted.
Syncthing's forum uses Discourse. The whole thing just smells of competence.
Dropbox/boxcryptor + MS Office. It’s of course necessary to use google drive for collaborative editing from time to time because it is so ubiquitous, but excel is still miles ahead of google sheets in terms of usability. Pages and Numbers are also pretty good for light use on the Mac and have free web versions for collaboration. The Dropbox desktop client is so much better than Drive in terms of CPU usage and straightforward sharing.
I have been using Microsoft OneDrive without issue for the past couple of months. The new Files On Demand feature works well. Of course this is only really helpful to Windows users which is a shame.