issue:
SOCKS proxy socks5h://127.0.0.1:9050 could not connect to fasttrack.debian.net (0.0.0.0:0) due to: general SOCKS server failure (1) [IP: 127.0.0.1 9050]
Or…
Err:4 http://HTTPS///fasttrack.debian.net/debian bullseye-fasttrack InRelease
500 SSL error: wrong version number [IP: 127.0.0.1 3142]
Or similar.
workaround here (update 2):
https://www.kicksecure.com/wiki/Operating_System_Software_and_Updates#fasttrack_repository_issues
(Whonix is based on Kicksecure.)