Google has such rampant influence that it’s difficult to block them completely with uBlock Origin or DNS solutions. However their corrupt surveillance can be reduced using some of the tactics and software in this article: https://simplifiedprivacy.com/how-to-reduce-googles-control-over-you/
For calendar and contacts I use EteSync since it uses E2EE just like Filen. Nextcloud is good but it does not have E2EE as a supported feature. There is a broken E2EE plugin for Nextcloud but only for files.
The Filen client works fine for me on Linux. It runs in the background and does not pop up after boot.
Oh ok, interesting. Then it may have been me being stupid. Guess I should try it again…