I updated to 10.15.7 this morning on my MacBook Pro 2019. My USB Keyboard no longer works. Worked fine before update. And, yes, it works on a desktop with 10.15.7. I use a USB-C adaptor that has 2 USB-C, HDMI, 2 USB-A ports. The USB-C works, the HDMI works, the USB-A works with my wireless mouse. But my USB wired (apple) keyboard stopped working.
I already tried many things to correct it:
reboot
reset SMC
reset PRAM/NVRAM
boot safe mode
Keyboard is still not working.
Last thing to try is install 10.15.7 combo updater.
It's downloading now.
Combo update installed. Apple wired USB Keyboard does not work.
I tried a non-apple wired USB Keyboard and it works fine in the same USB-A port.