Debian source.list query

Question

TLDR

1. Is it okay to edit /etc/apt/sources.list and change the entry from deb http://ftp.gb.debian.org/debian/ bullseye-security main contrib non-free to deb http://deb.debian.org/debian-security/ bullseye-security main?
2. Would I ever need ftp link?
3. How many source.list files should I have in /etc/apt?

thanks for help / explanations :)

Background info

When running updates I've been receiving this message:

W: Failed to fetch http://ftp.gb.debian.org/debian/dists/bullseye-security/InRelease  Could not resolve 'ftp.gb.debian.org'

I read this which suggested not using the ftp, but also says:

If you're using it now, please switch to either the deb.debian.org CDN or a country-based DNS name such as ftp.us.debian.org, ftp.ca.debian.org, ftp.uk.debian.org, ...

Noticed I was wrongly using ftp.gb... (great britain?) so I changed to ftp.uk... but got this:

E: The repository 'http://ftp.uk.debian.org/debian bullseye-security Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Therefore changed to:

deb http://deb.debian.org/debian-security/ bullseye-security main
deb-src http://deb.debian.org/debian-security/ bullseye-security main

...and now updates fine. But just wanted to check this is okay in case my system for some reason needs the ftp link?

Also is it normal to have this many sources.list ?

puppydog@woofwoof:/etc/apt$ ls -l
total 36
drwxr-xr-x 2 root root 4096 Feb 18 09:17 apt.conf.d
drwxr-xr-x 2 root root 4096 Jun 10  2021 auth.conf.d
-rw-r--r-- 1 root root  150 Dec  6  2021 listchanges.conf
drwxr-xr-x 2 root root 4096 Mar 28  2021 listchanges.conf.d
drwxr-xr-x 2 root root 4096 Jun 10  2021 preferences.d
-rw-r--r-- 1 root root 1166 Feb 18 10:22 sources.list
-rw-r--r-- 1 root root    0 Dec  6  2021 sources.list~
drwxr-xr-x 2 root root 4096 Feb 18 09:15 sources.list.d
-rw-r--r-- 1 root root 1168 Feb 18 10:22 sources.list.save
drwxr-xr-x 2 root root 4096 Feb 18 10:20 trusted.gpg.d

I have Debian GNU/Linux 11 (bullseye) x86_64 5.10.0-21-amd64

Answer 1

1. Yes.

2. No, I can't see why you would.

3. There's one sources.list file, that apt consults. In your directory there are also two backup files (sources.list~ and sources.list.save), obviously ignored by apt. There's also a directory sources.list.d/ which may contain files with the extension .list, that are also consulted by apt.