Replying to this for posterity’s sake. The issue has now been resolved. It was, indeed the HDHomeRun Docker causing the issue. It took over port80 when the author of said docker updated it due to Silicon Dust releasing a GUI for the DVR hardware. Unforseen consequence he has stated on GitHub after I opened an issue.
In order to access the webgui since the docker took over port 80 the following commands were used:
nano -w /boot/config/ident.cfg
then looking for the PORT line entry and changing it to a random number and saving the file.
/etc/rc.d/rc.nginx restart
Then typing in the IP:Newly Assigned Port of the UnRaid server into Edge / Firefox. Going into the Docker tab, stopping the offending Docker and then unchecking "autostart"
Reverse the commands above, changing the PORT line entry back to the default of 80 and rebooting the server allowed access once again.
CoZ's post in WebGUI after reboot no longer loads/connects was marked as the answer