Okay, I'll have to ask, trying to add this to Android Studio .. I got:

implementation "com.esotericsoftware.spine:spine-libgdx:3.5.51.1"

in the correct place, I can see the package..

Edit: Let me purhaps ask this first: is that line all that should be needed?

But when I drop the "com\esotericsoftware\spine" folder for the test files for spine into the core folder, then most of the imports shows up grayed out..

Making it impossible to run it ..

I'm out of ideas how to fix this atm. What information should I provide? I could pack the whole file and send it?

Okay, I had a series of unfortunate things happening, but your answer was the correct one ..

When I edited the line to:

implementation "com.esotericsoftware.spine:spine-libgdx:3.6.53.1"

then it removed 3.5.51.1 and instead put the example files I had put into core, as the library.

.. and it just kept getting worse with stranger things happening, in the end I just deleted the whole project and added libgdx and the correct spine version right away, and what would you know .. it works ..only took me 17 hours to fix

Android Studio is a bit wonky ^^;; Anyway, thanks for putting me on the right track.