Note that OnlyOffice is a Russian clone of MS Office. Its Russian branding P7 is still sold to Russian government and military. They didn't stop business with Russian government and opened offices in Latvia and Singapore to continue West presence. The clients are not fully open source either. You cannot independently build it. It is quite shady.

There is WPS from China with similar issues.

So your options are limited. LibreOffice sucks ass with any serious document. On Windows GUI bugs are annoying as hell. KDE's Calligra is slowly rotting.

I made the exact search as you did and decided to get a perpetual MS Office license. No other way around unfortunately.