[atlimar]

It supports external displays, just not on any port

[pseudosavant]

I was going by Asahi's own support page: https://asahilinux.org/docs/platform/feature-support/m1/

It seems that external displays are only supported on HDMI (e.g. Mac Mini) but DP Alt mode is still listed as WIP so I'd assume MacBook's with only USB-C (all of them?) can't support an external display.