The article mentions the lack of a swipe keyboard, which is an issue for me.

There is an option though: Heliboard with a custom swipe configuration applied (which is apparently sourced from Google, I'm not sure how "grey" that is).

It definitely works as a swipe keyboard, but it's just not as good as GBoard. I will persist, however. I hope that it's learning at least...

Check out FUTO keyboard (it's only ok). Or install GBoard, download the language of interest, and then disable network access to it

I'm using Ginger, which works well. Once I used it once, it downloaded the dictionaries, and I could revoke network access.