Thanks so much for playing!
The gallery contains full res images of all in-game backgrounds and CGs- to unlock the entire gallery you would need to go on all four possible dates for Nissa, Niels, Khara and Aksel.
Our dev team doesn't have many Macs to test on ourselves so it's difficult to find Mac-specific bugs but you can join our discord to report bugs and get support: https://discord.gg/UVdtGDMWMg