Yes, this is still possible with a Duet 3. Once you attach every Duet via USB, it will show up as a serial port that you may use for sending codes one by one.
if you prefer a network connection, you could use Telnet, too.
You can query full namespaces via M409 K”sensors” F”d99vn”. The new object model will be documented soon.
First a boot screen and then Chromium + Duet Web Control. However, there is a wide range of different displays out there and some may require additional configuration steps before they can be used.
FAT or FAT32, one partition