This is not a call for help. It's just a shame the whole bundle does not work. I am happy that at least the Krondor part had an easy work-a-round.
1- To play Betrayal at Krondor, just forget about the standard launching method;
> Go to the subdirectory: \SteamLibrary\steamapps\common\Betrayal Collection\Betrayal at Krondor
> Right Click on the KRONDOR.EXE file
> And pick the option to launch the game using the DOSBox program. You can install a version of DOSBox, or use the DOSBox.exe that can already be found in the \DOSBOX subdirectory of the game folder.
Note: No other edits should be needed to start the game. (I.E. A Picture listed under Artwork by same name: "Bundle is BROKEN 2023", shows how to do this.

2- However, for "Betrayal at Antana". You'll find at lease 10 different solutions on the WEB that 'might' make it work. (Be cautious of all the virus's out there.) The one method I found that had given me the highest hopes was the GOG updated Windows Installer, a msi file. But, for me - All the Hex, Regedits and patch updates I could find all failed to get the game to even start. Compatibility and video issue updates where also of no help. My understanding is these issues have been going on every since the Game was released. But, the seller obviously feels such an old game is a dead-horse and no-longer worth the effort. I don't feel right about asking for a refund on such an old game, just because 1/2 the bundle is toast - ?
I have resigned myself to just playing Krondor, and for $5 the old memories it brings back are worth it. NOTE: If you hung onto that old 486 PC or an older single core CPU PC, or if you can find a Stand-A-Lone version of Betrayal at Antana, maybe you could have better luck than I.
I hope this helps some.
Thanks for your time & Good Luck to my fellow wanderers of the Wilds of Krondor!