I tried Kbin, I just don't like their UI as much, plus no good Android clients that I know of, and I find things like upvotes vs. boosts really strange and confusing, its just completely unnecessary imo.
I use OpenBoard, its simplistic, but it works well for my needs, and its probably the best FOSS option I've seen. Florisboard has a lot of potential so I'll probably switch to that in the future when it improves, its FOSS and pretty close to Gboard.
My biggest issue is it currently doesn't have text prediction fully working. Once it gets that, I'll probably switch.