Yes. Very possible. An LLM could possibly be run locally or just sandboxed for only you. In my experience, I guess because there is less training data and fewer iterations, it tends to take longer and result in poorer outputs.
Microsoft could also let you control this but of course they do not want to.
.......
I switched to Openboard. After a few months, Its not as good yet as SwiftKey was, but it's also not sending all my text input to Microsoft.
The primary feature I miss from Swiftkey is the ability to insert a gif easily.