I know I already have issues with Safari on iOS so I assume you also don't have that in the lab but I'm surprised that Windows 10 is not represented in your lab.
So going to
http://nagios.vcaglobal.com nothing loads in the browser, just a message that it stops responding. Nagios XI was working, applied updates, and then would not load in Edge. I do need to check other computers / combinations.
I do get errors in the windows event log whenever I open Nagios.
The program MicrosoftEdgeCP.exe version 11.0.17134.523 stopped interacting with Windows and was closed. To see if more information about the problem is available, check the problem history in the Security and Maintenance control panel.
Process ID: 3468
Start Time: 01d4a90bfba52143
Termination Time: 15
Application Path: C:\Windows\SystemApps\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\MicrosoftEdgeCP.exe
Report Id: 83c7c8e6-d862-4c77-a5e7-a8da30e5d389
Faulting package full name: Microsoft.MicrosoftEdge_42.17134.1.0_neutral__8wekyb3d8bbwe
Faulting package-relative application ID: ContentProcess
Fault bucket 1486816943816134941, type 5
Event Name: MoAppHangXProc
Response: Not available
Cab Id: 0
Problem signature:
P1: Microsoft.MicrosoftEdge_42.17134.1.0_neutral__8wekyb3d8bbwe
P2: praid:ContentProcess
P3: 11.0.17134.523
P4: 5c2b0c7b
P5: a282
P6: 133184
P7: NO_PACKAGE
P8: browser_broker.exe
P9: 11.0.17134.523
P10: