Hello,Aidan Frey
Thank you for posting in the Microsoft community.
Please don't worry, according to your statement that you have already performed a fresh install, usually, the working of the on-screen keyboard doesn't have much to do with the hardware and BIOS, it belongs to the basic components of the system.
Therefore, I would like to further confirm your situation. Did you Reinstall Windows - Microsoft Support by the following method? Also, please unplug all linked external keyboards when doing on-screen keyboard input.
I look forward to your reply and I will discuss this further with you. Thank you for your understanding and cooperation!
Best Regards,
Rota|Microsoft Community Support Specialist