Unusual response to "sudo apt update"

After starting my Flidas liveUSB and trying to be able to update my applications I went to the terminal and entered the usual command (sudo apt update )and got the following response:


trisquel@trisquel:~$ sudo apt update
Hit:1 cdrom://Trisquel 8.0 _flidas_ - Release amd64 (20180417) flidas InRelease
Ign:2 http://archive.trisquel.info/trisquel flidas InRelease
Ign:3 http://archive.trisquel.info/trisquel flidas-updates InRelease
Ign:4 http://archive.trisquel.info/trisquel flidas-security InRelease
Err:5 http://archive.trisquel.info/trisquel flidas Release
Cannot initiate the connection to archive.trisquel.info:80 (2001:470:142:5::51). - connect (101: Network is unreachable) [IP: 2001:470:142:5::51 80]
Err:6 http://archive.trisquel.info/trisquel flidas-updates Release
Cannot initiate the connection to archive.trisquel.info:80 (2001:470:142:5::51). - connect (101: Network is unreachable) [IP: 2001:470:142:5::51 80]
Err:7 http://archive.trisquel.info/trisquel flidas-security Release
Cannot initiate the connection to archive.trisquel.info:80 (2001:470:142:5::51). - connect (101: Network is unreachable) [IP: 2001:470:142:5::51 80]
Reading package lists... Done
E: The repository 'http://archive.trisquel.info/trisquel flidas 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.
E: The repository 'http://archive.trisquel.info/trisquel flidas-updates 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.
E: The repository 'http://archive.trisquel.info/trisquel flidas-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.
trisquel@trisquel:~$

I am posting this because

• my IT knowledge is very poor
• I would like to know how do you understand this message
• I would like to know and what do you think I should do with regards to it.
• I think this post might help to solve problemes to some other Trisquel related users and/or developers.

Thank you in advance
Bubo