Hi there. I originally also only installed selenium, and got the same errors when trying to use Robot.
After doing a bit more digging, I tried install the robotframework-selelium library, which is clearly different from just the normal selenium pip installation.
https://robotframework.org/SeleniumLibrary/
pip install --upgrade robotframework-seleniumlibrary or pip3 install --upgrade robotframework-seleniumlibrary
Regards