Collabora and OnlyOffice setup documentation is really really bad… I have never seen such vague and ambiguous documentation in my life there is absolutely no step by step guide on how to do this, only snippets here and there that assume you are already familiar with the way things work in nextcloud… this is seriously ridiculous.
people looking for a solution like this are going to not want to spend the time getting something like this up and running, you cannot mention that you can edit documents within nextcloud without mentioning what a laborious and tedious process it is just to find the documentation in the first place then trying to decipher the “between the lines” explanations presented for every step. Never mind actually getting it to work. This would just not be a viable option purely based on the very poor documentation.