I just installed Unity 2020.3.48f1 and imported the PowerQuest 0.18.12 package and it has compile errors and does not load the PowerQuest window. If you close unity and reopen the project it asks if you want to enter safe mode to fix the errors. The console window did not show what the errors were.
I created a new project in Unity 2022.3.49f1 and removed the visual scripting package then imported the PowerQuest 0.18.12 package and the PowerQuest window popped up as expected.
I created a new project in Unity 6 Preview 6000.0.17f1 and removed the visual scripting package then imported the PowerQuest 0.18.12 package and the PowerQuest window popped up as expected.
I played the provided demo games on both Unity 2022 and Unity 6 fine. When importing the PowerQuest package with Unity 2022 and Unity 6 I set yes to convert all files.
Anyway, just thought I would mention that the version you recommend on the website was not working for me.