MIDI USB Host Interface for a USB keyboard and a legacy MIDI device with DIN connectors. - 5-pin MIDI DIN connector for a legacy MIDI device. They only have a USB port. n=MIDI channel (0-15). No PC required.
Introducing MIDI 2.0
The Truth About Bluetooth MIDI. Wireless MIDI? What about latency
ZVFOTN Upgrade Professional MIDI to USB Interface MIDI
Hosa USM-422 Tracklink MIDI to USB Interface - 6FT - Monkey Wrench
MIDI HOST Box Midiplus 16-Channel MIDI Interface Five-Pin UMH-10
Knot lets you use your USB MIDI keyboard to control your hardware
MOTU MIDI Express XT 8x8 USB MIDI Interface
WIDI Uhost - The 3-in-1 MIDI USB Solution over Bluetooth, by CME
TNP MIDI Cable Set to USB with Type C Adapter 2 in 1