They are not the only ones doing this. My BelCanto streamer is 4 yrs old and one year ago it stopped playing 24/192 files. So my answer from them was that I had to send it in and they would update it. It has a service USB but nope.
Mcintosh customer support
Requested Firmware update from Mcintosh for my ageing but still good sounding D150 Dac Mcintosh customer support virtually refused to supply Firmware v 1.02 with me . their answer was,,
( Unfortunately, company policy prohibits me from sending out firmware updates. We used to distribute them openly but they ended up on forums and were installed into incorrect units causing a massive influx in service repairs. At that point the company instituted the policy to no longer distribute them.)
it is so sad that Audio Giant like McIntosh do not care about their customers.