Only ON1 PHOTO RAW 2021 and our current 2021 products are compatible with Big Sur.
ON1 PHOTO RAW 2020 has not yet been updated for support with Big Sur.
We will be releasing a final update sometime in December for ON1 PHOTO RAW 2020 to include compatibility and new camera and lens profile support.
If you do not want to wait for the final ON1 PHOTO RAW 2020 update, you can upgrade to ON1 PHOTO RAW 2021 for full compatibility here
We will not be updating previous product versions (2019, 2018 etc) for Big Sur compatibility.