I installed ICSx5 from Play Store on my Samsung Galaxy S9 running Android 10 (stock). Upon first start, the app did not ask to be whitelisted from battery optimization.
According to FAQ , DAVx5 asks for whitelisting upon first start.
ICSx5, when switching to 4 h sync interval asks for whitelisting as well, but not for 1 day and 1 week sync interval.
In my case with once daily sync:Battery optimization on, sync does not occur after one day Battery optimization off, sync works every day.
The remote https-calendar has changes.
For the new user it would help and make the experience better to ask for whitelisting upon first start (for once daily sync).
Thank you for your consideration.