Can't access nextcloud over dDNS with Android from Local Network

Hello everyone. I am trying to access my Nextcloud from the Local Network over my dynDNS domain. This is no problem with my PC and my Chromebook accessing Nextcloud, on Android however, I always get a “ERR_NAME_NOT_RESOLVED” error.

Accessing in LAN over Nextcloud Local IP -> Success
Accessing in Mobile Internet with dDNS Domain -> Success
Accessing in LAN over dDNS Domain -> Error

Any suggestions? Thanks in advance!