This is the important paragraph on the article
Because Proton has no venture capital investors, we can take this additional step to secure the future. Swiss foundations do not have shareholders, so Proton will no longer be dependent upon the goodwill of any particular person or group of persons. Instead, Swiss foundations and their board of trustees are legally obligated to act in accordance with the purpose for which they were established, which, in this case, is to defend Proton’s original mission. As the largest voting shareholder of Proton, no change of control can occur without the consent of the foundation, allowing it to block hostile takeovers of Proton, thereby ensuring permanent adherence to the mission.
https://f-droid.org/packages/org.quantumbadger.redreader/
https://github.com/QuantumBadger/RedReader
I believe this one still works because it is designed for screen reader users, so they’re not paying for the API dings because of accessibility