I have upgraded lua in Homebrew from 5.2 to 5.3 in Homebrew/homebrew-core#21300. This broke lua support, so mpv now needs

depends_on "lua@5.1"

In Homebrew, @ formulae for older versions are temporary, so depending on lua@5.1 is not a viable long-term solution for mpv.

Some possibilities for mpv in Homebrew:

1. mpv becomes lua 5.3 compatible and switches back to depends_on "lua"
2. mpv switches from depends_on "lua@5.1" to depends_on "luajit" (if that works?)
3. mpv builds without lua support
4. something else that makes people :)