Grant his Samsung account limited access to your Location and turn off access to all the devices he doesn’t need.
Alternatively place his phone in a separate Location completely and get creative, possibly with third-party tools, to map his mobile presence into your main Location.
Hide the app via ‘Hide app’ in the Home screen settings (or wherever it is on his phone - I can’t imagine they’ve removed it.
I believe there may be age restrictions on SmartThings on later phones if you are using Samsung child accounts, which might confound the above.
For your first approach, I’m in the same boat with a Samsung Galaxy S22 as well. I’ve got over 100 devices. Do I need to go through each one and/or each routine if I were to disable or is there one universal “no access” button? The latter is what I need as the other potential user would be confused with the system configuration.
So I’ve taken this step (yes, it’s been a while). It looks like I can turn access off beyond the control of devices, but I’m still running into two “limits.” First, the other person still sees device history- maybe no way to get around this, unless I turn all devices off? Also, trying to get the presence (Samsung) to show up separately. I can see my Iphone, but unclear if the other’s samsung triggers presence. I can see the users for notifications, but the only presenceI see if my iphone. Ideas?.