Ubuntu 20.04 upgrade : "Please install all available updates for your release before upgrading" even after packages updating

Hello ! :)

I would like to upgrade my 18.04.5 Ubuntu to 20,04. Of course, before doing it, I’ve updated all installed packages :

sudo apt update && sudo apt -y full-upgrade && sudo apt autoremove

But even after this I have the “Please install all available updates for your release before upgrading” error.

So I try to check why, who and where there is some unupdated packages with this command :

apt list --upgradable -a

Returned this :

php-recode/bionic,now 1:7.2+60ubuntu1 all [installed,upgradable to: 2:7.4+73+ubuntu18.04.1+deb.sury.org+1]

So now, I try to update that php-recode module. Can’t found any prompt after 15 minutes of Google search so I try to reinstall it instead. :

sudo apt install php-recode

Returned this error :

Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 php-recode : Depends: php7.4-recode but it is not installable
E: Unable to correct problems, you have held broken packages.

That begins to be a bit too much for my modest autodidact Linux admin capacities, so this is why I seek for some help to solve this issue. :)

I don’t have really interest into upgrading to 20,04 but I’m a bit perfectionnist and psychorigid so I don’t like not having the last version.

Thanks. :)