I haven’t but I’ve looked briefly into other keyboards such as the Fossify keyboard (pretty sure it was that one, could be wrong), but the problem is the keyboard was broken for a period of like 3 months or something on specifically GrapheneOS I believe because it didn’t support something called direct boot or something…? Don’t quote me on the details but basically people were locked out of their phones for that entire period because the keyboard wouldn’t launch on boot for people to enter in their passwords.
I looked up the keyboards you mentioned just now and in terms of looks they are definitely great looking and miles ahead of the AOSP one. I just don’t want to lock myself out of my phone if I can help it, so that’s why I am afraid of switching from the AOSP keyboard. I’ve heard similar (though not as severely punishing) issues in regards to switching from other stock AOSP apps on GOS such as the clock or phone apps.
Sorry can’t provide any information on this as I basically immediately flashed GOS on the phone like two days ago and haven’t really switched to it seriously just yet. I am still in the experimentation phase for now.