u/Horror-Associate-959

Against the majority of advice from this forum earlier, I loaded OpenCore Legacy Patcher and then Sequoia to my old iMac just to see what would happen. Now it won't boot up under OpenCore EFI, and when I choose the hard drive to boot up I just get the circle with the slash. Not a disaster, as this is one of several computers we own and all files are backed up to an external drive. But would like to at least get it back to where it was. Any solutions? Or should I just throw it away at this point?