That's interesting, so if the phone is connecting via the local IP it maybe something on the PC do you have another laptop or PC you can check as well?
If you try the following from a CMD Prompt
If you have telnet installed, as its not a default install on W10 try the follow:
telnet 192.168.1.1 80
telnet 192.168.1.1 443
192.168.1.1 assuming that's the IP of the UDM.
Does it refuse the connection or does it give you a black screen?
Also under control panel, Internet Options, Connections, LAN Settings - Automatic Detect is Selected and Proxy is blank assuming you don't use one.
I had to enable telnet, but I get a blank screen with a flashing cursor, that means it has accepted the connection right? That was on both ports. I have 3 PCs in total connect via ethernet, none them are able to access it via local IP. Auto detect settings is enabled and proxy is off/blank.
I had a brainwave and decided to test safe mode with networking, I can access the local IP in safe mode. I had already tried disabling my antivirus/firewall, Kaspersky, and that didn't help, what else can be running that's causing an issue on all 3 PCs?
I had a second brainwave, Kaspersky is the only thing connecting all 3 PCs. Despite having disabled it to test, I decided to just uninstall it instead. Now I can connect. It was Kaspersky! Upon further investigation on one of the other PCs, I discovered that the issue was it was scanning all encrypted traffic on applications, by allowing an exclusion for the router IP on Chrome, all is well. The difference between the two firmwares I was using is the new ones moved to Unifi OS and now use HTTPS for the local IP connection, the old firmware was just HTTP.
I appreciate the help, thank you.