Surprised noone has mentioned OnlyOffice here: https://www.onlyoffice.com/ . We use it via the integration I wrote for Alfresco: https://github.com/cetra3/onlyoffice-alfresco
Never heard of OnlyOffice! They had a good comparison between them and libreoffice/collabora: https://medium.com/onlyoffice/onlyoffice-vs-collabora-a-crit...
If it had been a good comparison, it would have listed pros and cons of both solutions, rather than only pros for one, and only cons for the other.
The "comparison" really only points out three issues:
Collabora runs an instance of Libreoffice on the server. This must be taken into account when considering resource limits when scaling, and latency and bandwidth to the client(s).
Collabora's handling of OOXML (.docx/.xlsx/.pptx) is much worse than OnlyOffice's. You must take them at their word for this!
For collaborative editing, modes (bold/italic/font sizes etc), Collabora uses the same state for all clients. You must take their word for this. I also tested Collabora very briefly (using NextCloud's demo[1]), and the toolbar is client side, which means it could very well be that modes are not shared.
Of course, none of this is particularly surprising considering it was posted by OnlyOffice themselves.
[1]: Instant trial on https://demo.nextcloud.com/