My question/concern - for something as straightforward as a USB MIDI interface - would be "Why does it need a driver?"
From the Knowledge Base article on the Roland site:
https://www.roland.com/us/support/knowledge_base/206872093
The UM-ONE MK2 can be connected to a computer in two different ways, depending on the setting of the small switch labelled "COMP" or "TAB."
- COMP: This mode requires that you install a Roland driver on your computer for the UM-ONE MK2 to connect. Using this option you can take advantage of Roland's FPT processing technology which provides for faster MIDI processing speeds.
- TAB: This mode allows the UM-ONE MK2 to use the USB MIDI Driver that is built into your computers operating system, and does not require that a Roland driver be installed. This is useful if you have an OS for which there are no Roland drivers available.
The Roland driver can be used, but it appears that you do not
need to use it, so people making music on unsupported operating systems can still use the interface.
Perhaps the real question should be, why would someone
want to use the Roland driver and I suspect the answer is that the Roland driver might offer a better trade off between accurate detection of the MIDI signal and low latency.
Being US MIDI "class compliant" would be my #1 requirement for a MIDI/Audio interface.
Perhaps I need to try the UM-ONE MK2 with my linux laptop, which doesn't have a Roland driver and confirm that it works without one. I'm pretty sure there is no Roland driver available for linux and I certainly never installed one.
Update: The Roland UM-ONE MK2 works without the Roland driver on linux and I was able to connect the 5-pin MIDI from my keyboard to the UM-ONE MK2 and map the Roland usb MIDI interface to my audio samples and presets.
Back to the original question, step #1 is to try your M-Audio MIDI to USB adaptor without a driver - maybe that works without any problems. It isn't very clear if this interface was working in the past and what changed.
M-Audio have some troubleshooting info here:
https://m-audio.com/kb/article/1619