Hi Oskar - I'd love to propose a product idea to you, i'd love to buy something like this or the Mac if it were available. I had this on my linux laptop (https://man.archlinux.org/man/xtrlock.1.en) but it is surprisingly difficult to find for Macs -- something that locks the computer but still allows you to see the screen. This would be ideal for log windows, dashboards, etc.
Separately, if there is something like this already from a reputable MacOS appstore ecosystem i'd appreciate knowing about it from anyone.
What you're asking for is called "kiosk" mode.
Here's a random app I found: https://www.mackiosk.com/
I don't think this is quite the same thing as a kiosk setup, though depending on your specific goals you may find a kiosk-based solution to be an acceptable alternative.