My only complaint with OnlyOffice is that it's so insanely slow. Navigating the UI feels like it's running at 20fps or something. And loading up large excel sheets with thousands of rows often straight up crashes the program, or at least causes it to lag a huge amount when scrolling.

It's like this on my 2 PCs and my work PC too, even my gaming desktop which is more than capable of running a basic program like spreadsheets.

Libreoffice on the other hand is really fast, it's a breeze to work in. I also find the toolbar system in Libreoffice to be much easier to use when finding stuff like formulas or formatting functions.