Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::24) ,Network is unreachable) [IP: 91.189.88.142 80

So I just now did a fresh install to Linux Mint 20, but this problem was also present in Linux Mint 19.3. Every time I try to do a apt-get update or apt-get upgrade or even download software from the software manager I get an error. The same thing happened when I tried to update what the update manager recommended.

I found that I can upgrade or update if I keep running the command sudo apt-get update/upgrade after every failed attempt. As each update/upgrade stops at a certain percentage, when I run the command again it continues from that same percentage and by doing the update/upgrade a few times it finally completes.

This is the error I get when I tried downloading VLC from the software manager. It first says:

Failed to download package files
Check your Internet connection.

And the details are :

Failed to fetch http://archive.ubuntu.com/ubuntu/pool/universe/s/sdl-image1.2/libsdl-image1.2_1.2.12-12_amd64.deb Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::24). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::18). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::23). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) Could not connect to archive.ubuntu.com:80 (91.189.88.152), connection timed out Could not connect to archive.ubuntu.com:80 (91.189.88.142), connection timed out [IP: 91.189.88.142 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/pool/universe/s/sidplay-libs/libsidplay2_2.1.1-15ubuntu2_amd64.deb Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::24). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::18). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::23). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 91.189.88.142 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/pool/universe/libs/libspatialaudio/libspatialaudio0_0.3.0+git20180730+dfsg1-2build1_amd64.deb Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::24). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::18). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::23). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 91.189.88.142 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/pool/universe/s/srt/libsrt1_1.4.0-1build1_amd64.deb Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::24). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::18). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::23). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 91.189.88.142 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/pool/universe/libs/libssh2/libssh2-1_1.8.0-2.1build1_amd64.deb Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::24). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::18). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::23). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 91.189.88.142 80]
Failed to fetch http://archive.ubuntu.com/ubuntu/pool/universe/p/pupnp-1.8/libupnp13_1.8.4-2ubuntu2_amd64.deb Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::24). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::18). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8001::23). - connect (101: Network is unreachable) Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 91.189.88.142 80]

…and so on.

The two specific error values of error which appear everywhere are 2001:67c:1360:8001::23 and 91.189.88.152. The software sources my machines uses right now are:

(Main) http://packages.linuxmint.com
(Focal) http://archive.ubuntu.com/ubuntu

I tried changing the Focal sources to many different ones but no success. And I even messed up with the source.list files present in /etc/apt/source.list.d before and had to fresh install Linux due to many problems. So I really do not know what to do here and have found many others with the same problem.

$ sudo apt-get -o Acquire::ForceIPv4=true update