A good solution may be, to give Mac users a free Horizons pass for PC as sort of damage reduction, so they can spent the Horizons money on a windows copy for bootcamp.
At least, that would be a nice gesture, when refund is not happening and it would mean no costs for Frontier - so in some cases a win - win, while it still is a sad and bad thing for others.
I started playing on a mac, but made the jump to a gaming PC, when Horizons was announced. Nowadays i enjoy Elite in VR, so i have made my goodbye from gaming on Mac a long time ago. Still, i feel sad, for everyone who stayed by the flag-pole to the bitter end.
o7 fellow CMDRs