I still use Thunderbird, but at v52, because I want a local copy and archive of all my emails. It's also better to use compared to most webmail interfaces, particularly Gmail which is terrible.

Why v52, you might ask? Because I don't have time for updates to break my shit and v52 is the oldest version that supports TLS1.3. I do not like the new interface. At all. It can die in a fire.