Cannot Select Audio Device (resolved)

1) Start program from AppImage on Ubuntu home an/or use the appimage install feature and run from Installed Apps.
2) With no configuration changes create a score from scratch or load in a working score from 3.6.2
3) With start measure selected tap the spacebar to play.
RESULT:
A create loop range start bar appears, no play bar appears and the score does not play although there are instruments selected in the score AND in the mixer.
Note1 I'm a beginning MScore user who had only been using 3.6.2 for a few days. That version is fully functional on my machine.
Note2 Unlike 3.6.2, 4.0 (release- this reporter does not let me select other than "dev" and "Project" selections are non-sensical) does not allow me to select an audio device in Preferences I/O where "System Default" is the only selection.
Note3 I use a Behringer U Phoria as my audio/MIDI I/O for the machine which works fine with 3.6.2 and Audacity. The I/O page detects and accepts both MIDI In and OUT from this same device.

Conclusion: Inability to detect or select the Behringer as an audio device appears to disable all sound features in the program including playing single selected notes, ranges or the whole score. As a consequence I also cannot use Muse Sampler although it's detected in the "Diagnostic" menu. It is my hope you are able to scan and/or select more audio devices in future updates. Until then I have to keep using 3.6.2 although I can appreciate the AI detection in the new Properties and look forward to using that.