I have 3 errors in terminal when typing "sudo apt update"

[Akito]

@Aren_Tigranyan

does not have a Release file

Repository no longer has a release file

I am unable to screenshot when in the synaptic package manager but have copied and paste, The repository 'http://gb.archive.ubuntu.com/ubuntu disco Release' does not have a Release file.Updating from such a repository can't be done securely, and is therefore disabled by default.See apt-secure(8) manpage for repository creation and user configuration details.The repository 'http://gb.archive.ubuntu.com/ubuntu disco-updates Release' does not have a Release file.Updating from such a repository can…

Bistol. Repository no longer has a release file

My OS System is Ubuntu 64-Bit 20.04 LTS gnome version 3.36.2 My problem is Unable to download repository updates but general updates still download its seems I have corrupted the synaptic package manager on my system. My network is working o-k. This appears to have happened during the installation of my Epsom printer XP 455. which is still not working properly. Being new with ubuntu I have no idea how I caused this corruption or how to repair the situation, can you help much appreciated if you …

Not connecting to internet

The first thing to do after installing Linux Mint 20 is to get connected to the internet. Which my computer just won’t do. So, doing your 14 Things to do…is not possible. My other desktop, on which I installed LM20, runs perfectly and after installation connected to the internet automatically. I’ve tried everything to get connected on my 2nd desktop but nothing works.