Make sure to backup regularly. I don't know how good OnlyOffice is these days, but it definitely has (had?) a terrible history of quality control. We migrated off it a couple of years ago after losing several days of work due to severe (and, as it turned out, widely known) bugs in how it handled changes/document version tracking.
replyOnlyOffice is not really open source. They say they are but they also add impossible conditions to their license. (you are forced to use their logo, but you are also not allowed to use their logo.)
replyThat doesn’t bother me. I’m just looking for a free office program that runs offline and works well.
replyIt looks like the Euro Office suite will improve upon it when it launches and remove the remaining downsides to it.