Getting Error In "apt update" command...

[Sancho Godinho]

Get:4 http://packages.cutefishos.com bullseye InRelease [5,902 B]
Err:4 http://packages.cutefishos.com bullseye InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:5 https://mirrors.ustc.edu.cn/debian bullseye InRelease [116 kB]
Get:6 https://mirrors.ustc.edu.cn/debian-security bullseye-security InRelease [44.1 kB]
Hit:7 https://mirrors.ustc.edu.cn/debian bullseye-updates InRelease
Reading package lists... Done
E: Failed to fetch http://packages.cutefishos.com/dists/bullseye/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://packages.cutefishos.com bullseye InRelease' is no longer signed.
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.

[Le Bao Nguyen]

I also have same problem on my Ubuntu

[Le Bao Nguyen]

Anyway, if you want to update Cutefish components, do it manually by compiling them from source code.