To always show emails in reverse chronological order (latest on top) in Thunderbird, go to View > Sort by and then make sure that Date and Descending are checked.

If you cannot see your menu bar, press F10. You can then go to View > Toolbars and then make sure that the Menu Bar item is checked.

[This is for Thunderbird 115.0.1 (64-bit) for Windows 10.]