==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release):  1.5.0
- Deployed with iRedMail Easy or the downloadable installer?Installer
- Linux/BSD distribution name and version: Bullseye
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MariaDB
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

For anybody running into some problems with Upgrading Sogo and /or some unmet dependencies.

Update your sogo-nightly.list in /etc/apt/sources.list.d/ to

deb https://packages.inverse.ca/SOGo/nightly/5/debian/ bullseye bullseye

Make a apt update and if necessary a apt install sogo sogo-activesync

Did the trick for me.

Greets, mike