No lua5.4 support in Ubuntu 20.04

I have been happily using master and daily builds to get the bleeding edge features under development. However I now have the same lack of lua support that is alluded to in this post for users of 3.6.

Thank you, @wpferguson for your work, and I do note that the underlying cause is lack of lua5.4 packages for Ubuntu 20.04 as you point out on github.

I have managed to install from .deb packages lua5.4 onto my Ubuntu 20.04 system and will attempt to roll my own darktable. However I thought other Ubuntu 20.04 users on master might appreciate knowing why lua just stops working altogether, hence this post here on