It wouldn’t make sense to buy another audio interface to get mpu-401 compatible connections. Besides the fact that you would have to constantly switch from one device to another it will only have 1 in&output. If you have multiple devices you would like to control via midi in your setup it makes more sense to buy a dedicated midi interface with enough in/outputs to satisfy your needs. That way you can keep using your Lynx for high quality audio and still control your midi devices. To actually record the audio generated by the external device you’ll also have to connect it to an audio input of course.
Here’s a few examples of midi devices. Prices range from €100 to about €300
icon CubeMi 5 USB MIDI interface 5x5 MIDI interface
Motu MIDI Express 128 8x9 MIDI interface
iConnectivity mio10 MIDI interface 10x10 MIDI interface