Is the Polyend Play MIDI compatible?

Yes, it is. In fact, it is a very capable and intuitive MIDI sequencer. It can both send and receive MIDI messages over its dedicated mini TRS Type B MIDI ports and over the bidirectional USB Type-C port.

The MIDI Channel for both MIDI TRS and USB outputs is a selectable per-step in the MIDI sequencing mode with the use of a Sample/Folder knob.