Converting an old iMac to a 5K display

Last year my 2015 (or possibly late 2014) iMac died after a decade of service. Around the same time I acquired a new Mac mini. Unlike the iMac, the Mac mini doesn’t have a built-in monitor. I needed to acquire a new one. Unfortunately even newer displays in my price range would be a quality-of-life step down from the iMac screen I was migrating away from. New 5K monitors are $800+ and better…