Okay so this is just a little bit complicated, but given our current engine, any Mac build on Steam won't accept anything below 11.0 (apparently).
We should still be able to release a build compatible with MacOS 10+ here on Itch, just like the prologue.
We'll let you know if this turns out to be false somehow, or if we find some way around this (admittedly, we haven't looked into it too hard yet) We're sorry for any inconvenience!