Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - Bugs & Technical Problems macOS currently known issues and limitations

If you disable HDR, does the gamma adjustment help in the graphics options?

Try browsing to the ~/Documents/Larian Studios/Divinity Original Sin 2 Definitive Edition folder and delete or rename the graphicSettings.lsx file, to get the game to recreate it the next time it is started (unless that was already included in the files you tried manually removing).
For the App Store version, the path is: /Users/<UserName>/Library/Containers/com.larian.dos2/Data/Documents/Larian Studios/Divinity Original Sin 2 Definitive Edition