Emails alone to WiiM would be pointless as they wouldn't include your device logs. Any issue should be reported to Wiim via the more/feedback section in the WiiM Home app, clearly identifying in the subject line that you're on the Qobuz Connect beta e.g. "Qobuz Connect Beta: Connection issue", with the body of the feedback explaining the issue in more detail with screenshots etc as appropriate. Your device logs will also be sent when you submit the feedback.
Edit: as above, contacting Qobuz would also useful, but I'm not aware if they've instructed testers how to submit diagnostic info