apt install "*" method in Ubuntu 20.04 does not work

Ubuntu 20.04 introduced Apt 2.0

From the Release Notes:

New Features

• Commands accepting package names now accept aptitude-style patterns. The syntax of patterns is mostly a subset of aptitude, see apt-patterns(7) for more details.

Incompatibilities

• The apt(8) command no longer accepts regular expressions or wildcards as package arguments, use patterns (see New Features).

I have reported this as bug to launchpad - https://bugs.launchpad.net/bugs/1860366 against Ubuntu 20.04 LTS.

You can still use apt-get for this purpose:

sudo apt-get install "python3*"

will do what you (and really me) want. We need to change our habits here.