Follow up-
I found both the Tech Armor Ballistic Glass 3D Curved Screen Protector Designed for Samsung Galaxy S21, and the LK Tempered Glass Screen Protectors, will work with the Otterbox Defender. I ended up going with the LK only because the Tech Armor screen protector has a "cut-out" for the fingerprint sensor. It's not a hole in the protector but there is a circle over the sensor that I found distracting. I don't use the fingerprint sensor to unlock my phone, so I wasn't worried about it preventing the sensor from working.