Basically extension is working well because default card's background is not set as transparent. If you will go in this way by specifying f.e. --ha-card-background as rgba(0, 0, 0, 0.6) then you can easily notice that background is added twice - to the whole card and also to child cards.
There is an easy fix for that:
in lines 131 and 155 you need to add:
ele.style.background = 'none';
it does exactly the same like for borders ;)
Basically extension is working well because default card's background is not set as transparent. If you will go in this way by specifying f.e.
--ha-card-background as rgba(0, 0, 0, 0.6)
then you can easily notice that background is added twice - to the whole card and also to child cards.There is an easy fix for that: in lines 131 and 155 you need to add:
ele.style.background = 'none';
it does exactly the same like for borders ;)please check screenshot for reference:
PR: https://github.com/ofekashery/vertical-stack-in-card/pull/144