Solution was to connect from iPad to server using the FQDN pointing to the public IP of Cloudron.
Unclear why I couldnt connect via private IP, but I was using local DNS pointing the FQDN to the private IP, so I switched that to the public ip. I think that is what fixed it.
@girish thanks for the tip on the UDP scan, port was open via UDP on private IP.
benneic@MacBookPro ~ % sudo nmap -sU -Pn -p 19132 192.168.1.100
Starting Nmap 7.95 ( https://nmap.org ) at 2025-05-17 08:37 AEST
Nmap scan report for # (192.168.1.100)
Host is up (0.0025s latency).
PORT STATE SERVICE
19132/udp open|filtered unknown
Nmap done: 1 IP address (1 host up) scanned in 0.32 seconds
