How to not miss mail that arrives when I'm not at the computer?

Using Ubuntu 18.04 with KDE Plasma.

When a new mail arrives Thunderbird plays a sound and shows a notification, but when I'm not at the computer at that time I just miss new mails as there is no other indicator that a mail arrived. This used to be fixed by the New Mail Attention addon which made Thunderbird's icon flash in the panel until clicked, but "New Mail Attention is incompatible with Thunderbird 60.2.1". What now?