Cannot resolve .local address from dietpi

I have googled this but am not good at networking, so your help is much appreciated.

Problem:
Cannot ping any .local addresses from my dietpi.

Context:
I have a rasperry pi 4b with Raspbian and a pi zero w with Dietpi (7.5.2), and a desktop running Pop OS. All of them have avahi-daemon installed and running.

Observation:

  • I can ping from my desktop to my 4b using hostname.local & vice versa (rasp-4b.local / pop-os.local).
  • I can ping my dietpi on the zero from the 4b using dietpi.local
  • I cannot ping my 4b from dietpi on the zero using rasp-4b.local
  • I can ping my 4b from dietpi on the zero using the full ip address for the 4b
  • dig lookups resolve all .local addresses successfully (included below)
  • I also noticed that on my router admin page showing attached devices, my rasp-4b is listed next to its ip but dietpi is not listed next to its ip

Further details:
From my /etc/nsswitch.conf - this is identical on the 4b (raspbian) a nd zero (dietpi)

passwd:         files
group:          files
shadow:         files
gshadow:        files

hosts:          files mdns4_minimal [NOTFOUND=return] dns
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

From my /etc/resolv.conf on the dietpi (I noticed it doesnt say ‘# Generated by resolvconf’ like it does on the 4b)

nameserver 9.9.9.9
nameserver 149.112.112.112

From systemctl status avahi-daemon:

 avahi-daemon.service - Avahi mDNS/DNS-SD Stack
     Loaded: loaded (/lib/systemd/system/avahi-daemon.service; disabled; vendor preset: enabled)
     Active: active (running) since Sun 2021-08-29 03:21:18 BST; 14min ago
TriggeredBy: ● avahi-daemon.socket
   Main PID: 461 (avahi-daemon)
     Status: "avahi-daemon 0.8 starting up."
      Tasks: 2 (limit: 991)
        CPU: 762ms
     CGroup: /system.slice/avahi-daemon.service
             ├─461 avahi-daemon: running [dietpi.local]
             └─463 avahi-daemon: chroot helper

Aug 29 03:21:18 dietpi avahi-daemon[461]: Joining mDNS multicast group on interface lo.IPv6 with address ::1.
Aug 29 03:21:18 dietpi avahi-daemon[461]: New relevant interface lo.IPv6 for mDNS.
Aug 29 03:21:18 dietpi avahi-daemon[461]: Joining mDNS multicast group on interface lo.IPv4 with address 127.0.0.1.
Aug 29 03:21:18 dietpi avahi-daemon[461]: New relevant interface lo.IPv4 for mDNS.
Aug 29 03:21:18 dietpi avahi-daemon[461]: Network interface enumeration completed.
Aug 29 03:21:18 dietpi avahi-daemon[461]: Registering new address record for fe80::bc27:edff:fe20:aeb4 on wlan0.*.
Aug 29 03:21:18 dietpi avahi-daemon[461]: Registering new address record for 10.0.0.130 on wlan0.IPv4.
Aug 29 03:21:18 dietpi avahi-daemon[461]: Registering new address record for ::1 on lo.*.
Aug 29 03:21:18 dietpi avahi-daemon[461]: Registering new address record for 127.0.0.1 on lo.IPv4.
Aug 29 03:21:19 dietpi avahi-daemon[461]: Server startup complete. Host name is dietpi.

From dig command run on the zero (dietpi):

[rohdks@dietpi ~] $ dig -x 10.0.0.150 @224.0.0.251 -p 5353 +short
rasp-4b.local.
[rohdks@dietpi ~] $ dig -x 10.0.0.130 @224.0.0.251 -p 5353 +short
dietpi.local
[rohdks@dietpi ~] $ ping rasp-4b.local
ping: rasp-4b.local: Name or service not known