0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded. How can I upgrade that 1 package, or at least know which is?

I have tried many different solutions found around this and other websites, such as sudo apt update && sudo apt upgrade sudo apt list --upgradeable sudo apt full-upgrade sudo apt dist-upgrade and no information nor update of the package is displayed. I also tried aptitude update and checked the log and no information about the package is displayed. Any ideas on how to identify this package? My guess at this point, is that it might have something to do with the sources.list file. Any comments on this? I have Linux Mint with the latest distribution Ulyana / Focal. Thank you very much!