the one thing I'd find my 10-year-old MacBook Pro useful for, running xcode, is no longer an option because it now requires a newer version of macOS than I am allowed to run on a 2012 rMBP.
this bites ass, Apple, and you should be ashamed of yourselves.
@mdhughes I suppose that hiding old versions in a room with a sign on the door that says 'beware of the leopard' is better than nothing...
@djsundog LITERALLY Beware of the Leopard (10.5).
@djsundog This is a problem I've run into as well. :/ You can get older versions of xcode (occasionally through... questionable means), and I have done, but then you run the risk of the software you write not being able to run on the latest iDevices, and... sigh.
I dream of, one day, being able to afford a new Mac so I can actually learn and use Swift.
dyke 
@djsundog Maybe you can hackintosh it and run a newer osx.
@silverhax I really should give this a try at some point, just on principle haha
@djsundog You can still acquire old xcodes from
https://developer.apple.com/download/all/?q=xcode
Needs a freebie dev account.