"Currently" is not a valid response. Re-open this, provide the feature, or state that it will never happen. Stating that it is currently not an option does not merit a "Completed" tag. Other privacy respecting applications(1) allow for GCS-free notifications, WHY(would also be a valid response) can't Protonmail?
(1): Riot comes to mind, as does Nextcloud, Feeder, DAVx, AndStatus... All of these are open source too, get some code ideas from them, and implement that.
"Currently" is not a valid response. Re-open this, provide the feature, or state that it will never happen. Stating that it is currently not an option does not merit a "Completed" tag. Other privacy respecting applications(1) allow for GCS-free notifications, WHY(would also be a valid response) can't Protonmail?
(1): Riot comes to mind, as does Nextcloud, Feeder, DAVx, AndStatus... All of these are open source too, get some code ideas from them, and implement that.