One may replace the keyboard, but the underlying "input method" framework is still under OEM's (in this case, Samsung's) control: That is (afaik), they could key-log just fine regardless of whatever keyboard one may install / use.

I've tried both anysoftkeyboard and openboard, and liked openboard layout better but wanted swiftkey like support from anysoftkeyboard. Looking at reddit fossdroid I discovered the one fitted me better as a closer to openboard with swiftkey support : FlorisBoard

FlorisBoard is really nice. Among all of the FOSS Android keyboards, I've found the gesture typing on FlorisBoard to be the most accurate.

https://github.com/florisboard/florisboard