making wordpress gallery responsive

I’m using a 4 column native wordpress gallery on my homepage: https://www.peace-ed-campaign.org/ (see just below the slider).

When viewed on mobile, the 4 columns/images remain side-by-side and shrink to the point of being useless. I’d like the mobile responsive to adjust to either 2 or 1 image…

I’ve seen several threads here on this… but all answers date back to 2018. None seem to work anymore. Does anyone have any suggestions?

Other threads I’ve tried:

How to Make WordPress Default gallery responsive on mobile?

Making WordPress Gallery (.gallery-item) Responsive?

Currently trying this with no luck: