I would very much appreciate this functionality as well. Coming from a Huawei phone and more recently a LineageOS device, the lack of push notification support without google services is an annoying issue. Many other push notifications for messaging apps do function without GSF and implementing a similar design with ProtonMail is essential for independent operation. This is especially true for privacy-conscious users who prefer devices without google services installed.
I would very much appreciate this functionality as well. Coming from a Huawei phone and more recently a LineageOS device, the lack of push notification support without google services is an annoying issue. Many other push notifications for messaging apps do function without GSF and implementing a similar design with ProtonMail is essential for independent operation. This is especially true for privacy-conscious users who prefer devices without google services installed.