Yes! I looked into languagetool last week to see if I could host it locally on my Synology. They have an interesting page about how, after setting up the initial 200MB install, one can enable n-gram checks[0], which requires an additional 8GB of storage and an SSD. I haven't tackled that yet, but it's on my list!
[0]: https://dev.languagetool.org/finding-errors-using-n-gram-dat...