I'm in

I changed the 'Legacy Support' to enabled, but...

Its not a straightforward start up.

As I remember it (I'm here now so I'll just try to remember it for you), I pressed the on button and got a black screen with a little prompt at the bottom saying 'press esc to get start menu'. It takes you to a list of available OS, two of which were identical 'Ubuntu...etc' directly beneath the OS Boot Manager (which I presume would have taken me to Win 10 because that's what it does anyway).

I selected the top Ubuntu of the two in the list and pressed enter. then Mint started up and asked me for my password.

So here I am - working in my installation of Mint

I'm happy with this, even though its a clunky way of starting up.

Lets face it - I'm never going to be selling this machine, as its the only one I've got for a couple of years yet, so the only thing that matters is that I know how to use either of the OSs on my system