PSA on how to get your PS4 save to work on the PS5 version
1.Boot up the PS4 version (make sure it updated to 4.0!)
2.On the main menu, go to My Rewards
3.Follow steps on screen to link to your GOG account (or create a new account)
4.Open the PS4 save you want to use
5.Create a new save file for the 4.0 version (this should save to the cloud now)
6.Open the PS5 version
7.Repeat steps 2 and 3
Your PS4 save should now be available to load in the PS5 version.