iFrame support for Central Admin?

We're using an on-premises version of SharePoint Server 2016, and since support for Internet Explorer expires in August, I'm observing how its loss affects our SharePoint site.

I just learned that support for iFrames doesn't work in Google Chrome or Edge Chromium for Central Admin. For all our other SharePoint sites, I only have to set the Site Setting's HTML Field Security to accept our internal domain for iFrame support, but can't find this setting in Central Admin.

I discovered this while attempting to add a New User Profile for a new employee and attempted to browse our existing profiles (that appear in an iFrame portal). But unlike Internet Explorer, I just get a message that says, "SharePoint refused to connect."

When I tried Googling/Binging different solutions, I was astonished nobody discusses this problem anywhere. Is this problem unique to on-premises SharePoint servers, but not Microsoft 365 sites?