Hi, you posted that you need help testing DAVx⁵ 2.5. I have a little bit of feedback for the updated UI.
I was confused about the two different ways to refresh: Pulling down and using the floating action button. It looks like clicking the action button synchronizes the events and pulling down refreshes the list of calendars but does not necessarily synchronize. If I recall correctly, this is a change to the previous version where pulling down synchronized all events. The assumption that those two ways do something different comes from the fact that they take a different amount of time. There is no clue in the UI that tells me what pulling down actually does.
I suggest to display a snackbar when pulling down, just like when you press the action button, that tells you what is actually refreshed. The snackbar is especially important if the data that is refreshed actually changed when comparing to the previous version.