There is a donate tab, which you should not see once when the application updates. You close the tab and it should stay gone. There is also a standard Thunderbird page that loads when the application starts. It to contains a reference to donation, but also contains information about Thunderbird and support.

Get messages should automatically initiate when Thunderbird starts. Then there is a cloud icon in the top of the folder pane that gets all messages for all accounts. Then there is a get messages icon in the toolbar which only gets messages for the currently selected account. It only ever did, but few people appear to have been aware of that. Generally assuming it got everything and complaining it was broken when it did not.