If you download Stardew Valley from Fitgirl you might encounter mentioned issue. Seems like Proton-GE no longer works.
If you facing issue like this just use Proton - Experimental.
Guide
- Open Lutris & Click the
+ icon (top-left)
- Select
Add Locally installed game
- Go to
Runner options tab
- Finally you'll see wine version, Select
Proton - Experimental
