Cryptpad.fr can be an office suite substitute in some (but not all) cases.
For me, it works for personal use, but not professionally.
Of course, google docs on a throwaway account in offline mode is always an option.
Agreed that onlyoffice and collabora are kind of weird and unattractive from various usability and privacy perspectives.
I've been keeping my radar up about this for a few years, I have not found a perfect solution yet.