[abawany]

I recommend looking at the list of devices recommended by one of LineageOS (https://wiki.lineageos.org/devices/), /e/ (https://doc.e.foundation/devices), or PostmarketOS (assuming the application will run on plain Linux vs. Android) to see if they will work for you. The tablets they recommend are often older models so you will likely have to find these used/refurbished. It might be easier to get a detachable or 360-hinge PC laptop instead (e.g. MS Surface) if the weight/dimensions/application work better for you due to the high flexibility that PC OS-es offer compared to Android. Alternatively, a ChromeOS device, most of which can run Android apps, are a much better bet with long support, respectable vendors, and good flexibility.