Upgrade from Ubuntu 18.__ LTS to 20.__ LTS, failed

[jordboal]

I tried 2 days ago to upgrade my Ubuntu 18.__ LTS directly to 20.__ LTS, but in terminal I got the error message line about the updating program (Noitifica'm si hi ha una versió nova de l'Ubuntu: Notify me if there is a new Ubuntu version) which was set to Mai: Never. I mended it setting to Per a versions de suport a llarg termini: For support long term versions. But afterwards I got the error message line about setting prompt to normal. I don' know how to mend it. Look it at the attached files (two screen captures).

[grahammechanical]

When running the do-release-upgrade command do not use the -d switch. That -d switch upgrades to a development release version. Ubuntu 20.04 LTS stopped being a development version when it was released during April 2020. This is why you see the messages:

There is no development version of an LTS available
To upgrade to the latest non-development LTS release

Regards

[Dennis N]

You set it correctly to notify about LTS versions. But, the -d is not used with regular release upgrades, so leave it off and use sudo do-release-upgrade command. Then it would find 20.04 LTS and offer upgrade to that.