Unfortunately, it still does not work for me without running the terminal command
xattr -c /Applications/GRASS-8.4.app
I initially tested by moving my existing copy of 8.4 to the trash. I got the Apple can’t verity this app message. Then i tried overwriting my working version of 8.4 with the new one. I got the same message. But worse, after running the xattr command, I then got the original message that ‘this app is damaged’. Running xattr does fix this. I will try to reinstall my own compiled (unsigned) version and see if I can get it running.