Now that Abandoned Ruins core is updated to 1.4.0, it seems one of the Breaking Changes mentioned has broken this mod. Every time I try to play, I get this:

Error while running event Silly-AbandonedRuins-2-0::on_init()
__Silly-AbandonedRuins-2-0__/control.lua:248: bad argument #1 of 2 to 'next' (table expected, got nil)
stack traceback:
[C]: in function 'next'
__Silly-AbandonedRuins-2-0__/control.lua:248: in function 'attach_ruin_set'
__Silly-AbandonedRuins-2-0__/control.lua:305: in function <__Silly-AbandonedRuins-2-0__/control.lua:300>

I had to modify two other ruins extension packs to fix the add_ruin_set > add_ruin_sets mismatch, so those work again, but this error is different and something I don't know how to fix without disabling the mod. Looking closer at the lua, line 248 has to do with small, medium and large ruins in some way, and line 305 has an issue with line 248's parent attach_ruin_set(should_delay) function, so the bug seems to be there, if my rusty code intuition is pointing me right.