I didn't test CalyxOS yet but I suggest you to try GrapheneOS, if you have a Pixel. I think it is really well done, the documentation is detailed and the team's attention about security, and so privacy, is rock solid.

I use lineage os for microG [0] myself, but can't find a good foss android keyboard. Is there such a thing?

[0] - https://lineage.microg.org/

Florisboard

thanks!