Also, you're not using an outdated browser by any chance, are you? :has() requires at least Firefox 121 or Chrome 105 or equivalent.

I think you can safely replace that long selector with .product-label--owned if that's the case.

Sorry for the late reply (I've been sick for the past few days now).

I actually tested it on the latest Waterfox, but I'm not sure which version of Firefox it's based on.

Anyway, thanks for all the suggestions. I'll give it another whirl when I'm feeling more up to testing things.