Hello. I use DAVx5 (local server contact and calendar syncing app) on an A7 tablet and A20e phone. All have worked from the day I had them (A20e for over a year). All of a sudden (on the 23/04/2021) they both stopped connecting to the synology server. Looking at the error message the reason is that the DNS didn't know were the named servers were; using the IP address solved the problem. Looking at various webpages it looks like that the tablet and phone are no longer looking at the local DNS when a host name is used; supposedly android hasn't been doing this for years, but I have had no problems till now. Everything works for my windows PC, using both ethernet and WiFi, and I have checked for firmware updates on my tablet, phone and router.
Galaxy calendar latest update, this morning, won't allow multiple alerts! I checked permissions hadn't changed. This is something I use all the time to remind myself multiple times leading up to an event. Therefore very frustrating not to have this feature.