It looks like the Outlook I am required to use at work. I disabled Thunderbird Autoupdate when I learned this was coming down the pike a couple of days ago on HN.
> Card View emulates a mobile interface list with multi-line support, offering a more comfortable appearance to reduce cognitive burden. (And because we want Supernova to feel familiar for veteran users, the legacy “Table” view is still available.)
So what's the problem? Just keep using the view you prefer.
Oh thank goodness. I love the look of Thunderbird, and was dreading this change. I hope there are options to retain the same density on the email list.