My YunoHost server
Hardware: Computer at home (amd64 / 16Gb RAM)
YunoHost version: 4.4.2.13
I have access to my server : Through SSH | through the webadmin | direct access via keyboard / screen
Are you in a special context or did you perform some particular tweaking on your YunoHost instance ? : no
Description of my (resolved) issue
Issue is resolved, mostly for providing help to other / enforcing your migration scripts 
Running migration tool (web gui) from 4.4.2.13 to bullseye, the process stopped.
After checking the log files, I found that dpkg failed due to a file that already exists (/etc/sudo-ldap.conf).
A simple rm /etc/sudo-ldap.conf did the job, and after a re-run of the migration process (also in web gui) everything went fine
For information, you’ll find the whole log at https://paste.yunohost.org/raw/azukajusol