During standard upgrade steps you might see the following error message.
sudo apt-get update
Hit:1 tor+https://deb.whonix.org buster-developers InRelease Hit:2 https://deb.qubes-os.org/r4.0/vm buster InRelease Get:3 tor+https://cdn-aws.deb.debian.org/debian-security buster/updates InRelease [31.1 kB] Get:4 tor+https://cdn-aws.deb.debian.org/debian buster InRelease [118 kB] Reading package lists... Done E: Repository 'tor+https://cdn-aws.deb.debian.org/debian-security buster/updates InRelease' changed its 'Suite' value from 'testing' to 'stable' N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details. N: Repository 'tor+https://cdn-aws.deb.debian.org/debian buster InRelease' changed its 'Version' value from '' to '10.0' E: Repository 'tor+https://cdn-aws.deb.debian.org/debian buster InRelease' changed its 'Suite' value from 'testing' to 'stable' N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.
To fix, run the following command. Note: You will see the same error again but it can be safely ignored.
sudo apt-get --allow-releaseinfo-change update
Run the usual apt-get update command again. Note: Now the error message will be gone.
sudo apt-get update
You can process upgrading as per usual.
sudo apt-get dist-upgrade
Related: Qubes bug report