What happens when you try to switch to a windowed mode?
Did you try lowering the game resolution or graphics settings, and seeing if that made a difference?
Try verifying local files: in the Steam library, right click on Divinity Original Sin Enhanced Edition and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Cache...' button.
With the GOG version, in the (optional) Galaxy client, select Divinity: Original Sin Enhanced Edition in the left column, then click on the More button, and in the Manage menu select 'Verify / Repair'.
There aren't any game created bug reports, but you can email supportdos@larian.com, with your system specs, a crash report and sampler output from when the games freezes restarting it after a crash, and a save (your latest, or one that seems more likely to have a problem, if applicable, or where it can be reliably reproduced).
To get system specs you can use the 'System Report' button from the 'About This Mac' Apple menu item or the 'System Information' app (in the utilities folder).
Crash reports are collected in the 'Console' application. Saves can be zipped by right clicking the folder(s) and selecting Compress, in the folder:
~/Documents/Larian Studios/Divinity Original Sin Enhanced Edition/PlayerProfiles/<ProfileName>/Savegames_patch
To get sampler output from the Activity Monitor:
1. Verify your Steam or GOG game cache (as suggested above)
2. Launch Activity Monitor
3. Start the game and get into a freeze state
4. Now Alt-Tab back to Desktop and check Activity Monitor. What do you see? How much CPU does the game consume?
5. Double click on the Divinity - Original Sin Enhanced Edition process and press 'Sample' button. Wait until Sampler is finished
6. Save sample output using 'Save' button