If you run Collabora in a separate container, and then point NC at it as your Collabora server.. it is considerably faster. I have no issues w/ it and use it all the time.
I read that when I first installed it (it's on the github)
Nextcloud's built-in collaborative editing packages (Collabora/CODE and OnlyOffice) only work on x86_64 systems with glibc, and therefore they are not compatible with our images.
Since I didn't saw a real use for me, I just forgot about it.
Thing is, for those who don't see it, when you do the initial install of NC (the initial step where you create the user and set the database, etc), there's an already ticked box that makes NC install the "default apps" and it includes Collabora apps.
Let me see if I can find a screen of it on the NET.