I just switched to the Halifax mirror and apt update. No errors! I also don't see any mention of "neutower" anywhere.
Get:1 https://dl.google.com/linux/chrome/deb stable InRelease [1,825 B]
Get:2 https://deb.debian.org/debian unstable InRelease [198 kB]
Get:3 http://debian.mirror.iweb.ca/debian sid InRelease [198 kB]
Hit:5 http://repository.spotify.com stable InRelease
Ign:6 http://linux.dropbox.com/debian sid InRelease
Get:7 https://dl.google.com/linux/chrome/deb stable/main amd64 Packages [1,082 B]
Hit:8 http://linux.dropbox.com/debian sid Release
Get:9 https://deb.debian.org/debian unstable/main amd64 Packages.diff/Index [63.6 kB]
Hit:4 https://cdn.liquorix.net/siduction/fixes unstable InRelease
Get:10 https://ftp.halifax.rwth-aachen.de/siduction/extra unstable InRelease [18.6 kB]
Get:11 https://deb.debian.org/debian unstable/main Translation-en.diff/Index [63.6 kB]
Get:12 https://deb.debian.org/debian unstable/main amd64 Contents (deb).diff/Index [63.8 kB]
Get:13 https://deb.debian.org/debian unstable/main all Contents (deb).diff/Index [63.8 kB]
Get:14 http://debian.mirror.iweb.ca/debian sid/main amd64 Packages.diff/Index [63.6 kB]
Get:16 https://deb.debian.org/debian unstable/main amd64 Packages T-2023-10-27-2003.31-F-2023-10-27-1404.20.pdiff [23.8 kB]
Get:16 https://deb.debian.org/debian unstable/main amd64 Packages T-2023-10-27-2003.31-F-2023-10-27-1404.20.pdiff [23.8 kB]
Get:17 https://deb.debian.org/debian unstable/main Translation-en T-2023-10-27-2003.31-F-2023-10-27-1404.20.pdiff [397 B]
Get:18 https://deb.debian.org/debian unstable/main amd64 Contents (deb) T-2023-10-27-2003.31-F-2023-10-27-1404.20.pdiff [1,825 B]
Get:19 https://deb.debian.org/debian unstable/main all Contents (deb) T-2023-10-27-2003.31-F-2023-10-27-1404.20.pdiff [2,664 B]
Get:19 https://deb.debian.org/debian unstable/main all Contents (deb) T-2023-10-27-2003.31-F-2023-10-27-1404.20.pdiff [2,664 B]
Get:18 https://deb.debian.org/debian unstable/main amd64 Contents (deb) T-2023-10-27-2003.31-F-2023-10-27-1404.20.pdiff [1,825 B]
Get:17 https://deb.debian.org/debian unstable/main Translation-en T-2023-10-27-2003.31-F-2023-10-27-1404.20.pdiff [397 B]
Get:20 http://debian.mirror.iweb.ca/debian sid/main Translation-en.diff/Index [63.6 kB]
Get:21 https://ftp.halifax.rwth-aachen.de/siduction/extra unstable/main amd64 Packages [93.4 kB]
Get:22 http://debian.mirror.iweb.ca/debian sid/main all Contents (deb).diff/Index [63.8 kB]
Get:23 http://debian.mirror.iweb.ca/debian sid/main amd64 Contents (deb).diff/Index [63.8 kB]
Get:24 http://debian.mirror.iweb.ca/debian sid/main amd64 Packages T-2023-10-27-1404.20-F-2023-10-27-0803.37.pdiff [16.4 kB]
Get:25 http://debian.mirror.iweb.ca/debian sid/main Translation-en T-2023-10-27-1404.20-F-2023-10-27-1404.20.pdiff [213 B]
Get:26 http://debian.mirror.iweb.ca/debian sid/main all Contents (deb) T-2023-10-27-1404.20-F-2023-10-27-0803.37.pdiff [2,961 B]
Get:24 http://debian.mirror.iweb.ca/debian sid/main amd64 Packages T-2023-10-27-1404.20-F-2023-10-27-0803.37.pdiff [16.4 kB]
Get:25 http://debian.mirror.iweb.ca/debian sid/main Translation-en T-2023-10-27-1404.20-F-2023-10-27-1404.20.pdiff [213 B]
Get:26 http://debian.mirror.iweb.ca/debian sid/main all Contents (deb) T-2023-10-27-1404.20-F-2023-10-27-0803.37.pdiff [2,961 B]
Get:27 http://debian.mirror.iweb.ca/debian sid/main amd64 Contents (deb) T-2023-10-27-1404.20-F-2023-10-27-0803.37.pdiff [959 B]
Get:27 http://debian.mirror.iweb.ca/debian sid/main amd64 Contents (deb) T-2023-10-27-1404.20-F-2023-10-27-0803.37.pdiff [959 B]
Get:28 https://ftp.halifax.rwth-aachen.de/siduction/extra unstable/main amd64 Contents (deb) [3,523 kB]
Fetched 4,592 kB in 42s (110 kB/s)
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
9 packages can be upgraded. Run 'apt list --upgradable' to see them.