I just can’t find a decent email client that looks like it’s from the last 20 years. Geary and Evolution both appear to be pretty modern but something about using Gmail with a Yubikey just doesn’t work and neither of them will connect to my account. Both on Fedora and OpenSUSE. Thunderbird works but it’s so old fashioned and Betterbird doesn’t look much better. What’s everyone else using?
Thunderbird + K9 Mail are my way to go, too.
Though I mostly do like the redesign, since it fixes some long standing issues with Thunderbird (e.g. not being able to select a multi line message view (“cards view”), instead of the traditional table view.) The search bar being always on top annoys me each time I open it, so I understand a more long time Thunderbird user might have more nitpicks. Almost all of the changes can be reverted through settings, which I find awesome.