You have three choices:
  1. Find the app on Play that someone in your situation said worked for them

  2. Buy a name brand mouse that identifies itself as a mouse instead of a generic HID device

  3. Buy or borrow a BT keyboard and connect it. Once you do, this setting will appear and you can have the onscreen keyboard always display. It's currently set to "hide" but the only way to access the setting to change it is to connect a BT keyboard.