So iLO3 is a bit long in the tooth, even with the latest firmware (from December 2020), it’s under the impression that TLS 1.1 and AES/3DES are the pinnacle of TLS.
There are a number of things you have to do to be able to talk to this beast with a “modern” browser (specifically, Microsoft Edge).
Enable IE mode
In Edge, go to edge://settings/defaultBrowser and make sure sites are allowed to be reloaded in Internet Explorer mode:
Mess with IE security settings
Click on Internet options and go to the Advanced tab in the window that appears, then scroll down and enable TLS 1.0 and TLS 1.1. THIS IS A VERY BAD IDEA IN GENERAL and should only be enabled while you are actually trying to access your iLO fossil.
Open the site
Now you can open the iLO server in Edge, you will get told that it can’t be connected to. Click the three-dot menu at the top right and click Reload in Internet Explorer Mode.
Remember to roll back
Once you have finished working on your iLO fossil, remember to go turn TLS 1.0 and TLS 1.1 off again in Internet Options.