I have the following error when running sudo apt-get update, kindly assist Clearsigned file isn't valid, got 'NOSPLIT'

Get:16 http://packages.microsoft.com/repos/code stable InRelease [9,890 B]     
Err:16 http://packages.microsoft.com/repos/code stable InRelease               
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Hit:17 https://packages.microsoft.com/repos/ms-teams stable InRelease          
Reading package lists... Done                                                  
E: Failed to fetch http://packages.microsoft.com/repos/code/dists/stable/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://packages.microsoft.com/repos/code stable 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.

this happens on a fully updated Ubuntu 20.04 where the normal system update commands ran OK yesterday

The repo has recently changed, you just need to change "vscode" to "code" in /etc/apt/sources.list.d/vscode.list or whatever it's called on yours.

Reference: https://github.com/microsoft/vscode/blob/e7647291206dbe540c0d5121889b4f9f9c9d43f7/resources/linux/debian/postinst.template#L43-L55