I just discovered that the SP-404MK2, when used in conjunction with a TRS-MIDI adapter “borrowed” from my OG Novation Circuit (if this is adapter-specific…), does not work. After extensive troubleshooting cluded in by a WIDI Jack which does offer a switch to control TRS MIDI type A/B switching inversion, I realized the blokas midihub supports only one mode of operation. This is a pity because it effectively requires that I order an additional widi jack just to provide the inversion (but also mostly relieved to benefit from one less cable this way 
Please correct me if I’m wrong about midihub support and/or whether someone can clarify that I should simply find an alternative MIDI-TRS adapter.
Hey, there’s only a single DIN-5 port MIDI connector standard, making Midihub able to swap the signals around would make it break the standard.
You should find a compatible DIN-5 adapter for your device. You can find a great summary on the TRS MIDI port types here: https://minimidi.world/
If you need to combine Type A and Type B ports, there might be someone selling an integrated adapter that does the conversion using only TRS jacks, but a conventional way would be to get Type A ↔ DIN5 and a DIN5 ↔ Type B adapters, and just use a DIN-5 cable between the devices.
I see, thanks for the clarification about the need for an alternative TRS adapter. It totally makes sense that you want to avoid breaking the DIN-5 MIDI standard.