Trouble with MDNS

Can someone help me getting my mdns to work? Raspberry Pi Zero with most recent image installed. I checked manually installing avahi-daemon and (that’s what is currently running) installing shairport-sync because it has it as a dependency installed via dietpi-software.

Service status:

● avahi-daemon.service - Avahi mDNS/DNS-SD Stack
   Loaded: loaded (/lib/systemd/system/avahi-daemon.service; disabled; vendor preset: enabled)
   Active: active (running) since Thu 2018-12-06 10:35:03 GMT; 8min ago
 Main PID: 937 (avahi-daemon)
   Status: "avahi-daemon 0.6.32 starting up."
   CGroup: /system.slice/avahi-daemon.service
           ├─937 avahi-daemon: running [DietPi.local]
           └─938 avahi-daemon: chroot helper

Dec 06 10:35:03 DietPi avahi-daemon[937]: Joining mDNS multicast group on interface wlan0.IPv6 with address fe80::ba27:ebff:fea5:7657.
Dec 06 10:35:03 DietPi avahi-daemon[937]: New relevant interface wlan0.IPv6 for mDNS.
Dec 06 10:35:03 DietPi avahi-daemon[937]: Joining mDNS multicast group on interface wlan0.IPv4 with address 192.168.1.200.
Dec 06 10:35:03 DietPi avahi-daemon[937]: New relevant interface wlan0.IPv4 for mDNS.
Dec 06 10:35:03 DietPi avahi-daemon[937]: Network interface enumeration completed.
Dec 06 10:35:03 DietPi avahi-daemon[937]: Registering new address record for fe80::ba27:ebff:fea5:7657 on wlan0.*.
Dec 06 10:35:03 DietPi avahi-daemon[937]: Registering new address record for 192.168.1.200 on wlan0.IPv4.
Dec 06 10:35:04 DietPi avahi-daemon[937]: Server startup complete. Host name is DietPi.local. Local service cookie is 4230641184.
Dec 06 10:35:05 DietPi avahi-daemon[937]: Service "DietPi" (/services/ssh.service) successfully established.
Dec 06 10:35:05 DietPi avahi-daemon[937]: Service "DietPi" (/services/sftp-ssh.service) successfully established.

Looks totally fine. But noone on the net (able to browse mdns) can see it. Tried iOS devices, windows with bonjour, linux with avahi-utils and another pi running raspbian. Example tests (local):

root@DietPi:~# ping DietPi.local
ping: DietPi.local: Name or service not known[/quote]
[quote]
root@DietPi:~# ssh DietPi.local
ssh: Could not resolve hostname dietpi.local: Name or service not known

But… it appears to resolve?

root@DietPi:/var/log# avahi-resolve -n DietPi.local
DietPi.local    fe80::ba27:ebff:fea5:7657
root@DietPi:/var/log# avahi-resolve -n Himbeere.local <- that's my other Pi running raspian stretch
Himbeere.local  fe80::5b09:d920:8400:a0e7
root@DietPi:/var/log# ssh Himbeere.local
ssh: Could not resolve hostname himbeere.local: Name or service not known

even avahi browse looks fine (Himbeere and mdns-VirtualBox are other avahi devices)

root@DietPi:/var/log# avahi-browse -at
+  wlan0 IPv6 91A5B7EBE8A4@DietPi                           AirTunes Remote Audio local
+  wlan0 IPv4 91A5B7EBE8A4@DietPi                           AirTunes Remote Audio local
+  wlan0 IPv6 Himbeere                                      SFTP File Transfer   local
+  wlan0 IPv6 DietPi                                        SFTP File Transfer   local
+  wlan0 IPv4 mdns-VirtualBox                              SFTP File Transfer   local
+  wlan0 IPv4 Himbeere                                      SFTP File Transfer   local
+  wlan0 IPv4 DietPi                                        SFTP File Transfer   local
+  wlan0 IPv6 Himbeere                                      SSH Remote Terminal  local
+  wlan0 IPv6 DietPi                                        SSH Remote Terminal  local
+  wlan0 IPv4 mdns-VirtualBox                              SSH Remote Terminal  local
+  wlan0 IPv4 Himbeere                                      SSH Remote Terminal  local
+  wlan0 IPv4 DietPi                                        SSH Remote Terminal  local

Note: Normally there are other MDNS advertising devices that i disabled for troubleshooting. So i think i can rule out router configuration problems.