Expand DKIM selector coverage or allow custom selectors

When DKIM tracking is enabled on a website, the list doesn't include Proton Mail's selectors (protonmail, protonmail2, protonmail3), so domains using Proton Mail show "No DKIM records found for any known selector" even when valid DKIM records are published.

Could you either add Proton Mail's selectors to the built-in list, expand the built-in list to cover other common mail hosting and transactional email providers, or let admins define custom/arbitrary DKIM selectors per website?