pairing of keyboard does not work during clean reinstall

I am doing a clean install of Sierra on my Macmini I am selling (had to press CMD-OPT-SHIFT-R) and now the process hangs on the step 'to pair a keyboard, turn it on and wait for your computer to pair to it'.

I use the keyboard that was paired to this same machine.

The Bluetooth keyboard is non-apple (TP), so I cannot keep the powerbutton pressed . . .

The keyboard was originally paired to this same macmini. Of course I did not unpair the keyboard before dong the clean reinstall of Sierra, and now it is not detected anymore.

1. Should I abort the clean install process (worried that this will damage the computer and it will not start up properly anymore like it was before)
2. Should I unpair a keyboard from another mac?
3. Should I go and find an old wired keyboard?

re 2 and 3: But if I cannot connect my existing TP keyboard do I then have to discard it?