Actually you can add a modern GPU to the old iMacs, they use an MXM GPU. I have upgraded my 2010 iMac to a 2012-era GPU from a Dell laptop to get metal support

Actually you can add a modern GPU to the old iMacs, they use an MXM GPU. I have upgraded my 2010 iMac to a 2012-era GPU from a Dell laptop to get metal support. I have also upgraded the CPU, Wifi card, and added 32GB of RAM to this 2010 iMac.