I agree that a Trello-style project board could fit nicely into the Proton ecosystem. Simple Kanban boards with tasks, due dates, labels, and collaboration would pair especially well with Proton Calendar.

It would be even more useful if cards could connect directly to calendar events and reminders while keeping the same privacy-focused approach as the other Proton services. A lightweight solution would probably be enough for many users without trying to become a full project-management platform. https://monkeymart.com.br/ is unrelated, but the idea of keeping everything connected within Proton makes a lot of sense.

This is quite a large request, so if positieve it will take time.
I tend to work a lot with Trello (a scrum/agile board application), and this is awesome and helps me structuring my work and projects.
When I considered Nextcloud, I learned they integrated "deck" which is similiar. a bit simpler, but verry well integrated into the nextcloud environment. So you could use attachments in mails straight into cards on the Deck Scrum Board, and deadlines on task-cards came into my calenders, and I really experienced the added value of that.

So, can Proton also consider adding a new proton app , similar to Deck and with an equal level of integration in the other Proton apps.

Kind regards
Marcel Collignon

This!