They're not that big of a deal, but my two biggest annoyances with RFP:
1. prefers-color-scheme is completely broken, even in the dev tools. Mozilla refuses to fix this in any way, it is allegedly "by design" that you have to disable all RFP protection if you're a web dev and need to test the dark color scheme of your website.
2. Similarly, RFP always vends your timezone as UTC with no way to change.
that's a great way to get even more fingerprinting potential, each additional switch is another bit of identification on top of the actual fingerprint itself.
1. prefers-color-scheme is completely broken, even in the dev tools. Mozilla refuses to fix this in any way, it is allegedly "by design" that you have to disable all RFP protection if you're a web dev and need to test the dark color scheme of your website.
2. Similarly, RFP always vends your timezone as UTC with no way to change.