I noticed that in My Ubuntu 20.04, I have some duplicate packages (from Ubuntu 18.04): Calculator, System monitor, etc. For instance, when I search for System monitor, here is the result:
In addition, the old packages appear with garbled-characters, when I open the old version it appears as follows:
However, the versions from Ubuntu 20.04 show up properly without that issue.
How can I get rid of those duplicated packages?