Owl is still the best option as far as I am aware.
For some things I guess I don't mind closed source from a small company, but my company mail probably isn't one of them.
Price: 10€. Starbucks really did a lot of damage here. 2 coffees should be 3€, not 10.
Calendaring through Lightning is incomplete and experimental.
In the "spaces" vertical toolbar on the left, Owl has added a Teams button recently, as well. It opens the Teams O365 app in a tab in Thunderbird, which I really like. I haven't had a chance to check if any meeting or audio features work there.