All ISO’s before cassini (including Artemis Nova LiveISO) use grub by default. Cassini is the first ISO to use systemd-boot by default. Perhaps that might be the problem with the Mac Book Pro.
I believe there is an option in cassini to optionally use grub.
EDIT:
See this URL for cassini’s release notes:
https://endeavouros.com/latest-release/
A blurb from that web site.
And it ships with these new features:
x86_64:
Added a choice of bootloaders as well as the ability to not install a bootloader
(systemd-boot is default selected)
Switched to dracut from mkinitcpio
Pudge