Hi, this bug indeed makes opensmtpd completely unusable for me (who sends mails unencrypted in the current year?).
As a temporary workaround for my setup I have re-added the bullseye repo in sources.list, installed opensmtpd=6.8.0p2-3, and set it on hold (echo "opensmtpd hold" | sudo dpkg --set-selections). Regarding a permanent fix: I think normally major version upgrades don't happen within a Debian stable release. Although considering that opensmtpd in its current state is basically unusable I personally don't think the usual concerns around major version upgrades apply.
