I also note /etc/exim4/update-exim4.conf.conf got overwritten without asking the user Y/N. I also note exim4-config contains #!/bin/bash scripts without Depends: bash.
D> Be sure the package passes Checkbashisms! JN> Which package? Is there a particular bashism you noticed? All the shell scripts in the exim* packages. Anyway please declare a Conflict with bash5, or better yet make the package finally installable. Thank you.