Instead of implementing per-user domain whitelists across all VPN apps, Proton could maintain a curated allowlist of privacy-respecting domains (like www.startpage.com) that are exempt from NetShield ad blocking.

This could be either:

enabled by default, or
offered as a single opt-in toggle.

Pros: Simple implementation (DNS-side only), consistent across all platforms, supports privacy-friendly business models.

Cons: Requires Proton to curate and maintain the list and some users may disagree with inclusion criteria or prefer maximum blocking without exceptions.