Resolve unmet dependencies?

Question

linux

https://askubuntu.com/questions/140246/how-do-i-re...
https://apt.postgresql.org/
https://www.pgadmin.org/download/pgadmin-4-apt/

sudo apt-get -f install
clean
autoclean
autoremove
update
upgrade
dist update + upgrade 
dpkg –configure -a   // OK

They didn’t help me anyway - it still gives out that

The following packages have unmet dependencies:
 pgadmin4 : Depends: python3-flask-babelex but it is not installable
                   Depends: python3-flask-gravatar but it is not installable
                   Depends: python3-flask-htmlmin but it is not installable
...

Tried the same thing with aptitude

The following actions will resolve these dependencies:

     Keep the following packages at their current version:
1)     pgadmin4 [Not Installed]
2)     pgadmin4-common [Not Installed]

Accept this solution? [Y/n/q/?] Y
No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 5 not upgraded.
Need to get 0 B of archives. After unpacking 0 B will be used.

This post is confusing

The following actions will resolve these dependencies:

     Keep the following packages at their current version:
1)     pgadmin4 [Not Installed]

1 - we're installing this package, how can it be a dependency?
2 - the following actions will help solve the dependencies, and from the actions only "do not install anything" is available based on the translation

Keep the following packages at their current version:

3 - so how can you install a package if it is a dependency of itself, and from the available actions we can only establish its impossibility to install its dependency on itself. Something like this.
The result is obvious

No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 5 not upgraded.
Need to get 0 B of archives. After unpacking 0 B will be used.
                                         
[email protected]:~$

What am I missing?