Smithsonian Channel HD? When will it be available?

I just switched to Xfinity from another provider and enjoyed Smithsonian Channel in HD for years.  I made sure to specically ask for Smithsonian when I ordered service.  I'm in the Chicagoland area and discovered it's only in SD.  This is unacceptable in 2019 not to have it in HD.  When will it be avialble?  That's the channel I watch most than all the others.