For those customers, I gave them an ‘application’ version that was just nw.js (basically chrome). Worked reasonably well for the customers that had somewhat recent OS on their desktops or terminal server.
Your customers sound like the smartest and most sensible people I've heard about in a while. The current way the Web is changing makes it almost impossible for in-house use in a large corporate environment. But at the same time, it's almost impossible to avoid it entirely; so instead do the smart thing and put a hard stop on it and refuse to hit the moving target.
I don't disagree. I feel like I'm caught in the middle. I personally prefer the old internet where websites could have simple design and typography and still be perceived to have value.