

Eh, my Nextcloud LXC container idles at less than 4.5% CPU usage (“max over the week” from Proxmox). I use PostgreSQL as the backend on a separate LXC container that has some peaks of 9% CPU usage, but is normally at 5% too.
I only have two users, though. But both containers have barely IO activity.
Running LanguageTool locally is a bit of a pain, with some manual steps. Plus you have to fetch some data files. You can find around a few projects like this one to make it easier to run LanguageTool.
And yes, as the poster mentioned, LanguageTool keeps some code exclusive to their paid version. There’s a bit of a tension because they ask people not to extend OSS LanguageTool with their paid features.
There’s also this interesting clone, but it seems abandoned.