I have a customer who is using eM Client beta 9 (the second beta) and has come across a problem when printing. The Print dialog gives an error that it is missing a plugin where a print preview would normally be, and will not allow them to print, even when clicking the print button. When pressing the Print using the system dialog link, nothing happens either. Currently, they are able to save to a PDF and then print the PDF as a workaround.
Not sure where to report problems for the macOS beta 9 and I can’t see it as a known issue.