Temporary workaround until ESET fixes this: Add the property as described in: https://developer.apple.com/library/content/qa/qa1734/_index.html
At own risk:
1. Close ESET Antivirus
2. Open Terminal
3. Navigate to correct folder: "cd /Applications/ESET\ Cyber\ Security\ Pro.app/Contents/"
4. Open Info.plist: "sudo nano Info.plist"
5. Scroll to botom and before the final /dict add the following:
6. Hit ctrl+x to quit and and y to save.
7. Restart ESET and notice how it only uses iGPU now