u/Leerachelc

Hi, I have seen online some printed/engineered QWERTY Keyboard attachments, likely designed for smartphones but does anyone know anything about how these work and might connect to a dumb(ish) phone? I can figure out the "making a case to connect it" part on a 3D-printer if necessary but in terms of the actual function does anyone know how it might connect if I got something like a flip phone with android capabilities? Like would it require Bluetooth or is it connected through the actual wiring & hardware? Any information would be helpful <3