Delete foreign packages in Migration to Linux Mint 20

Question

The new version of Linux Mint 20 has been announced and along with it a User Guide (migrated from this tutorial) to help us in the migration process.

Now, there are two steps which trouble me:

1- Purge PPAs and 3rd party repositories, which says:

...

• Click on Remove Foreign Packages.

• Select all foreign packages and click Remove.

...

2- Delete foreign packages which, says:

With the exception of packages you want to keep, select all foreign packages and click Remove

When I check all of the foreign packages installed (from "Menu -> Administration -> Software Sources -> Maintenance -> Remove Foreign Packages") I see there is a LOT of them.

I'm able to recognize some of these packages, but I'm not sure about most of them.

So,

What are the implications of not Removing the Foreign Packages?

Related, What if I remove accidentally a package that is needed by some app later on? Can I recover it? (I guess so, but I'm not sure if it is safe to do so)

What may be the best way to approach this?

---

Side note:

• I executed mintupgrade check and the output seems fine to me.
• I'm an intermediate experienced Linux user.

Answer 1

The implication of NOT removing foreign packages is, that they can't be updated. Since Mint doesn't know the structure of those PPAs, it can't change their entries in the apt list. Apps that have been installed from the foreign repositories will not be upgraded as well and might reference libraries that won't exist after the upgrade anymore.

Example:

You have "specialVideoApp" installed from a foreign repository which references libavcodec-5.2.0. After upgrade that app will still be there, but the library (which is part of the Mint system) was upgraded to libavacodec-5.2.3. Then this app won't work anymore. You would have to update it yourself.

If the packages are falsely marked as "foreign", as PoorYorik pointed out, it should make no difference - those packages are likely to be updated.

I've tried it on Mint 18 and I didn't get any "foreign" packages.

To sum it up: It will not hurt your new installation, if you don't remove those foreign packages - but it should be likely that some of those applications won't work after the upgrade.