I have exactly the same problem with my mid-2015 Macbook Pro 15” Retina (A1398).
I did replace the keyboard and the backlight (this is a huge hassle, and please note where every screw went if you are willing to try it.
When I reassembled my Macbook Pro, everything worked properly EXCEPT the left $@$*, control and option keys. Arggg! I have tried resetting the SMC using a USB attached mac keyboard..doesn’t seem to do anything.
I just downloaded another version of Catalina and will try installing on an external SSD and boot from a clean install to see if it is a software issue.
If anyone has any idea how to fix this, please post it. Thanks!