Ok. This jostled some things loose for me. I believe I've compiled Pd with the right flags. 
Apparently, I had failed to test the option /dev/midi2. I noticed when the keyboard
wasn't plugged in that only /dev/midi1 was listed. I'd still expect when using -alsamidi that
Pd would show Alsa-style labels like UMC404HD and MPKmini2, but I only recently switched to
Linux as my daily driver and hadn't experimented with MIDI yet.

Thanks to everyone who helped me to learn more about this subject.

Am 28. April 2022 15:37:31 MESZ schrieb Samuel Burt <composer.samuel.burt at gmail.com>: >Still no luck compiling with alsa-midi support. I must still be missing >something. > ALSA-MIDI will be builtin on Linux by default, unless you explicitely disable it (ALSA). You must tell Pd to use it at runtime. Either via the "-alsamidi" flag, or by selecting it in the media menu. You must *also* make sure that the number of MIDI-ports opened by Pd is "1" or more (in the MIDI-dialog, or via "-mididev 1"). The default is "0" for some reason (I might have been involved in that default, but can't remember...) mfg.sfg.jfd IOhannes