“Proton cannot even link to FAQ or customer support pages from its apps, as Apple believes it’s possible that users will then navigate from the support page to a pricing page and upgrade their accounts without paying Apple its fee.”
Proton joined the developer class action against Apple to block a settlement that would just pay out money. Apple’s own numbers in the Epic case showed a 78% margin on App Store fees. Ad-funded apps from Meta and Google never pay the 30%. Privacy apps that charge subscriptions do.