Hey there archibald t,
To clarify, do you have the option for "Allow Others to Join" enabled? If not, this will be the first step we recommend to help make sure you're able to use Personal Hotspot with another device.
Use the steps below to help:
On the device that provides Personal Hotspot, go to Settings > Personal Hotspot, then follow these steps:
Make sure that Allow Others to Join is on.
Remember the device's Wi-Fi network name and password that appear on this screen. If you want to change the Wi-Fi network name, learn how to change your device name.
If you're using an iPhone 12 model or later, turn on Maximize Compatibility.* Then try connecting your devices again to your Personal Hotspot.
Stay on this screen until you connect your other device to the Wi-Fi network.
On the device that needs to connect to Personal Hotspot, follow these steps:
Turn Wi-Fi off and back on.
Make sure that you connect to the correct Wi-Fi network. The network name is the same as the iOS device that provides Personal Hotspot and the Personal Hotspot icon
might appear next to it.
If you see a password error when you try to join Personal Hotspot, check the Wi-Fi password: On the device that provides Personal Hotspot, go to Settings > Personal Hotspot to see the Wi-Fi password.
If Personal Hotspot is not working on your iPhone or iPad (Wi-Fi + Cellular) - Apple Support
Take care!