Interesting feedback. Thank you.
One thing to keep in mind is that the Anyma Phi being monophonic connecting MPE controllers to play it is not necessary the first use case.
The USB MIDI Host is meant to allow the connexion of MIDI Class compliant device but it seems that this "standard" is still subject to various interpretation among MIDI controller manufacturer.
What we tested on our side among MPE device though are 2 of the one you listed:ROLI Seaboard Rise and Seaboard Block are working with the Anyma Phi Haken Continuumini was also tested but with the result you described with this "not enough power" message on the Continuumini although the power provided should be enough. We made a few attempts to check this was a USB software protocol trick (by rising the available power message) but with no success so far. We do not have any Linnstrument in our workshop yet so we couldn't make any test on this one. We weren't aware of the various speed available on this one. (This could make it a valuable test unit for our tests with the Omega). USB Hub is not really something we expect to work as the device is intended to manage one controller device.
One thing to keep in mind is that the main target of this USB MIDI Host port is to allow the use of the Anyma Phi with a controller which does not feature any DIN connector, so the expected MIDI speed is currently the standard MIDI speed.
The Anyma Omega will be done using a new generation board so there will be much more ressources available to manage a higher speed MIDI (and the merge and routing of MIDI coming from the various MIDI port: USB device, USB Host, DIN MIDI In ... and the "internal" command coming from the keyboard and ribbons, the CV/Gate signal etc.).
This is part of the necessary spec for the MPE compatibility of the Omega.
Once this would be done, we could then check what could be transferred back from the Omega to the Phi.