We have Nextcloud Hub 26 Spring (34.0.0) installed & have replaced the previously installed Collabora with Euro Office. It is working great & performance, client-side is much better. The only thing that we miss is the ability to add additional fonts easily like we could with Collabora in the GUI.
Is there anyway to do this with Euro Office - I understand there is no method in th GUI, but is there a way to do this manually?
Yes, there is. See here: Custom fonts - Euro-Office
In the context of Nextcloud AIO (which is docker based) - can this be done? If so how?
In theory, yes. In practice, however, as far as I can tell, there isn’t an straightforward, officially supported way to do it. Ideally, there would be an environment variable exposing /usr/share/fonts/custom as a volume mapped from the host inside the container.
This was already discussed for ONLYOFFICE > here < , but for reasons that were never fully explained, they decided not to implement it. However, in the thread a few worarounds are mentioned that should also work with Euro-Office.
Another option would be to run Euro-Office in a separate Docker container instead of using the one bundled with AIO.
Neither of these workarounds are particularly great, but I can’t see any other options at the moment.
I appreciate your reply, and here’s hoping that an easy practical solution is implemented soon. At our organisation - everyone really likes Euro Office over Collabora, performance-wise, the only downside is the font selection.
Maybe you could open a new discussion on the AIO GitHub about it. Technically, although Euro-Office is based on ONLYOFFICE, it’s no longer the same product. 
Also, since Euro-Office is now being developed independently of ONLYOFFICE, it might be worth checking whether there is already an open issue or feature request to implement this via the UI of the connector app. If not, consider opening one: Issues · Euro-Office/eurooffice-nextcloud · GitHub