ON1 confirmed that the next update to Photo RAW 2021 will have customizable keyboard shortcuts (Photo RAW 2021.5):
"Wouldn’t it be nice to have total control over your keystrokes? Well, coming in the next free update to Photo RAW 2021, version 2021.5, is the ability to assign all of your keyboard shortcuts to your liking. It’s also a huge benefit for our international customers. We’ve been working on this and a lot more. Stay tuned!"