After upgrading kde neon to focal base.
apt command gives me error.


sudo apt-get update
Get:1 http://archive.neon.kde.org/user focal InRelease [250 B]
Err:1 http://archive.neon.kde.org/user focal InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:2 http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu focal InRelease [250 B]
Err:2 http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu focal InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Err:3 http://security.ubuntu.com/ubuntu focal-security InRelease
Could not connect to security.ubuntu.com:80 (91.189.88.152), connection timed out
Err:4 http://in.archive.ubuntu.com/ubuntu focal InRelease
Could not connect to in.archive.ubuntu.com:80 (43.255.166.254), connection timed out
Err:5 http://in.archive.ubuntu.com/ubuntu focal-updates InRelease
Unable to connect to in.archive.ubuntu.com:http:
Err:6 http://in.archive.ubuntu.com/ubuntu focal-backports InRelease
Unable to connect to in.archive.ubuntu.com:http:
Reading package lists... Done
E: Failed to fetch http://archive.neon.kde.org/user/dists/focal/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://archive.neon.kde.org/user focal InRelease' is not 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.
E: Failed to fetch http://ppa.launchpad.net/oibaf/graphics ... /InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu focal InRelease' is not 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.

the issue has been fixed,it was a network issue.