Hello dryadsdad,
To start, you'll want to determine which actual model iPhone you're using. You mentioned "iPhone 12 SE (second generation SE)" in your description, which is two different models. The iPhone 12 is one model, and the iPhone SE is a different model. This is important to know, as this will determine if this is expected or an actual issue. An easy way to tell is just by looking at the front of the phone. If it's an iPhone 12, the screen will cover the entire front. If it's an iPhone SE, it will still have the "Home" button below the screen.
The Maximize Compatibility setting is available on iPhone 12 models and newer. If you are in fact using an iPhone SE (2nd gen), that model does not have the Maximize Compatibility setting in the Personal Hotspot options.
If Personal Hotspot is not working on your iPhone or iPad (Wi-Fi + Cellular)
Cheers!