The alternative to a company that is hiding real coupon codes and stealing affiliate marketing dollars?
Honestly, there's no good answer here because most of the work is manual, not automated, and there are a lot of opportunities for bad actors. It's just a bad model in general.
There are legit communities which already collect that information in structured ways. For example https://www.ozbargain.com.au/ is quite Australia-oriented, but could be turned into an extension bringing up the coupon codes automatically.
I don't think it exists today, but someone could make a crowdsourced extension like SponsorBlock. That also eliminate the concern about hiding promo codes for companies who pay.
Honestly, there's no good answer here because most of the work is manual, not automated, and there are a lot of opportunities for bad actors. It's just a bad model in general.