Get all Deck tasks into assignee's calDAV somehow

The Deck app will make boards available for calendars and tasks, which is fine—although it gets pretty unwieldy if you have a lot of boards.

If I have a teammate who has subscribed to a calendar in Nextcloud, and now she sees these tasks and appointments in her Outlook or Thunderbird/Lightning, that’s great; however, if I start a new board and assign something to her, realistically I can’t do that and then ask her to go into the settings in her calendar client, search for new calendars, and then add the calendar for that kanban board in order to see her tasks. That’s just not realistic.

Therefore, I’m hoping there is some way to get a user to subscribe to one calendar, and get all the tasks in there that are assigned to her—regardless of what board they’re coming from. This would mean either merging the board calendars, getting them under one umbrella calendar, or somehow syndicating specific tasks by asignee. I’m sure others have wonders about this, so what are our options?

An update: when I use the Deck app for Android, I can go to ‘upcoming tasks’ and it shows me all tasks on all boards that are assigned to me. This means it is possible to aggregate the tasks in this way. Now, I just need to know how to run this query, and how to get it to return the results in CalDAV format. Then, I could add that query as its own calendar.