Error NU1201 compatibility error with SDK versions

In the fabulous " Create a C# Application from Start to Finish - Complete Course" a 24 hours course that Tim Corey published in Youtube, I’m stuck and it is probably because its 4 1/2 years after its publication, I guess there’s something that has changed in the VS environment setup that causes the “run” command to fail in the build process if I create a reference from the TrackerUI project to the TrackerLibrary project (4:57:38 in the video).
It shows the following ErrorLog:

Severity Code Description Project File Line Suppression State 
Error NU1201 Project TrackerLibrary is not compatible with net6.0-windows7.0 (.NETCoreApp,Version=v6.0). Project TrackerLibrary supports: uap10.0.17763 (UAP,Version=v10.0.17763) TrackerUI C:\Users\xxxxxxx\source\repos\TournamentTracker\TrackerUI\TrackerUI.csproj 1

I’ve tried changing the SDK version in the TrackerUI project to every possible option, but it doesn’t work at all…has anybody any clue on how to solve this issue?

Hi, at last I managed to work it out without having to do all the work from the very beggining once again: it seems there were 2 different issues with my setup that caused all the fuss.
First I installed the “.NET Upgrade Assistant” extension to be able to verify that both the library project and the UI project where consistents in their versions.
Then I created a new solution, a new library project, copied all the code from the initial solution and verified that all was in the right SDK version.
Afterwoods, I created a new UI project and “imported” all the previous project froms via “Add existing item”, what spared me the tedious job of having to create all the forms again. I verified also the SDK version with the assistant.
After all this, tried to run it and EUREKA! it works.
What did I learn from this? I’ve got to pay better attention to what you do at the beggining of the projects, specially at the names you decide, because afterwoods if you touch anything, you will have really annoying problems. Hope this helps somebody sometime!