SiriusXM not working with Bluetooth speaker

I recently signed up for SiriusXM and had hoped to play music on my UE BOOM2 bluetooth speaker from their web site. The music plays for 30-40 seconds and then goes silent. The music “scroll bar” continues to clock off the track, even though there’s no sound. (There’s no problem if I play through the computer’s built-in speaker.) I recently updated to Safari 15.0, so that might be relevant, but my SiriusXM subscription is new, so I never tried it on an older version. Amazon Music doesn’t have this problem. [2017 27-inch iMac w/ macOS 11.6]

I have problems with a UE Boom, and a UE Megaboom, when listening to Zoom meetings on iPad. The sound frequently cuts out. Sometimes, pressing the volume button works to regain sound. Sometimes I have to switch the speaker off, then on again. Of the 2, the UE Megaboom is less problematic in this regard.

Changing the volume or switching the BOOM2 off and on again doesn’t work for me. Closing out the SiriusXM window and restarting it works, but again, only for 30-40 seconds.

Interesting, because I have been having problems with SiriusXM as well. I use the iOS SiriusXM app to AirPlay to my stereo HomePods (the original large size). In the past I’ve had no problems. Recently, however, whenever I try I get maybe a couple of minutes before the sound stops. This probably has nothing to do with Bluetooth, although I’m not entirely sure how the iPhone connects to the HomePods. So something has changed in the changes to iOS/HomePod OS 15 and my switch to a 13 Pro, but I’m not sure what. (I did recently have a Bluetooth problem with my AirPods Pro and iPhone, and had to erase/reconnect them to solve it.) AirPlay using the Music app works fine, but I haven’t tried any other app recently beside SiriusXM. For now, I use my AirPods whenever I want to listen to SiriusXM.

As an added datapoint: The BOOM2 is my “designated” iMac Bluetooth speaker, but I also have an OontZ Angle 3 which is paired to my home stereo. When I paired the OontZ to my desktop, the same thing happens (30-40 seconds of music, then silence). So it’s apparently nothing to do with the Bluetooth speakers themselves.

A kinda crappy workaround: I had an old Miccus Home RTX bluetooth extender that I reinstalled with a wired input to my desktop’s headphone jack. After pairing to my BOOM2, Sirius now plays continuously with only occasional (but very irritating) half-second audio dropouts.