ONLYOFFICE Desktop Editors v7.4 is already available, offering the majority of the improvements of ONLYOFFICE Docs v7.4. Read this post to find out more.
ONLYOFFICE Desktop Editors v7.4 released: form templates gallery, plugin manager, new print settings and more.
Isn’t OnlyOffice proprietary software?
You’re thinking of FreeOffice.
It’s licensed under AGPL
Didn’t try it but it looks like they also provide an installable offline version under the AGPL: https://github.com/ONLYOFFICE/DesktopEditors