I tried running a 2nd instance of Roblox simultaneously on macos 15 with another account but this shows up, if my mac can handle it then why can't it just let me do it? If I have two copies of an app like Roblox in separate User/Applications folders, macos moves them to the /Applications/ folder.
Sometimes it won't run apps claiming to be corrupted, so I then have to do sudo xattr -cr /Applications/someapp.app in the terminal and they run perfectly fine. It always nags me if I download apps from anywhere but mac app store. Some of these messages can only be gotten rid of by disabling system integrity protection, but then macos blocks you from running MAS apps due to having "permissive security".
I don't daily drive macOS anymore, I switched to Linux on my M1 mac where I can do whatever the hell I want.
I think this is only conditionally true... A good AMD based system on say Fedora with a GPU that's at least a year old ... you really won't have much of a problem on Linux in my experience or much to fix.