Update to Catalina with iMac mid 2011

Catalina support is limited to a short list of mac models and is not hardware specification dependent. Even with upgraded hardware Apple does not support Catalina on a 2011 iMac anymore than they do a 2012 Mac Pro (and unlike the Mac Pro there are no officially supported GPU upgrade options).

No sorry, a Mid 2011 iMac can only be updated to 10.11 High Sierra. If you need or want to run Mojave, Catalina or Big Sur when it is released, then you will need to buy a new or newer Mac.

Gotta buy a new Mac if you want Catalina or beyond. Your iMac (and my 2011) are simply too old.