I’ve used ONLYOFFICE on my nextcloud server as well as the desktop editors, and I really like them.
One small thing I don’t like about the desktop editors is they’re merged into one app. While this is convenient and you only have to launch one app to edit anything, I think it would be better to have them “split,” per se. If you want to write a word document, click on the docs app in your system’s app launcher. Presentation? Slideshow app. Something much more like LibreOffice/MS Office.
While I say having split apps would be better, having a sort of “home” app (much like the current ONLYOFFICE app) would still be good. From here, you have access to all 3 apps.
I’m on Ubuntu 20.04 LTS/Pop!_OS 21.04, currently on desktop editors 6.4.2