install libssl-dev on Ubuntu 20.04.1 (upgrade from 18.04.1) reports unmet dependecies with 1.1.1g-1+ubuntu18.04.1+deb.sury.org+1

I have upgraded from Ubuntu 18.04.1 to Ubuntu 20.04.1 (forced release upgrade), then while installing php.7-4 it was necessary to also install libssl-dev, that gave the following unmet dependencies:

sudo apt install libssl-dev
The following packages have unmet dependencies:
 libssl-dev : Depends: libssl1.1 (= 1.1.1f-1ubuntu2) but 1.1.1g-1+ubuntu18.04.1+deb.sury.org+1 is to be installed

• I have disable the repositories: ondrej and certbot. The remaining repositories are the default for focal fossa (20.04.1)

• Clean up repository e.g (apt update --fix-missing)

But sill the same problem.

Solution 1:

The issues is with the letter version of libssl1.1 (= 1.1.1f-1ubuntu2) that needs to be downgraded. It was simple to do it with synaptic instead of apt install as follows:

sudo aptitude install libssl-dev

he following NEW packages will be installed:
  libssl-dev{b} 
0 packages upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 1.582 kB of archives. After unpacking 8.005 kB will be used.
The following packages have unmet dependencies:
 libssl-dev : Depends: libssl1.1 (= 1.1.1f-1ubuntu2) but 1.1.1g-1+ubuntu18.04.1+deb.sury.org+1 is installed
The following actions will resolve these dependencies:

     Keep the following packages at their current version:
1)     libssl-dev [Not Installed]                         



Accept this solution? [Y/n/q/?] n
The following actions will resolve these dependencies:

     Downgrade the following packages:                                                   
1)     libssl1.1 [1.1.1g-1+ubuntu18.04.1+deb.sury.org+1 (now) -> 1.1.1f-1ubuntu2 (focal)]



Accept this solution? [Y/n/q/?] y
The following packages will be DOWNGRADED:
  libssl1.1 
The following NEW packages will be installed:
  libssl-dev 
0 packages upgraded, 1 newly installed, 1 downgraded, 0 to remove and 0 not upgraded.
Need to get 2.900 kB of archives. After unpacking 8.087 kB will be used.
Do you want to continue? [Y/n/?] Y

Basically don't accept the proposed solution and carry on the a package downgrade