So here was the solution for me coming from synology assistance (Malek was super nice to help me):
1/ On the NAS, in control panel, “external access”, tab DDNS : create a synology address… it will be something like that: <name>.synology.me
2/ On the NAS, Set a fixed ip address on the local network to the nas : to do that, go to control panel/network/tab:network interface and modify the LAN line “manual ip config” the line IP address with the number you want (for me 192.168.1.24)
3/ on your box, open ports 5001 (connect to it through its local address and modify its NAT configuration. open a port for your nas in TCP port 5001
so here, the nas is accessible fro the outside on its caldav
4/ on the android DAV5X, open it, add a account, select URL and there add put the URL: https://<name>.synology.me:5001/caldav/<your_id>/aiioyb/
and enter your <your_id> and your password (the one to connect to your nas, at the id session).
Calendars do not show up
After successfully retrieving the CalDav collections from icloud.com I don’t see the calendars anywhere in my calendar app:
There is not much in the log file giving me an idea what could be the culprit:
Would be glad for any suggestion.
Did you try another calendar app?
I see you have a MIUI device. Xiaomi is a bit problematic because they changed a lot on the Android base firmware. They added an autostart feature that prevents DAVdroid from sync. Please have a look here:
Look at the “Autostart, App auto-launch (and similar)” section.
Does it solve your problem?