A lifesaver. Most comprehensive posting I’ve seen on the subject.
You can do the same for Mozilla Thunderbird
edit>preferences>advanced> config editor
In the Config Editor, search for “mailnews.thread_pane_column_unthreads” by typing it in at the top. When you see the preference, change the value from “True” to “False” by double-clicking on it, or by right clicking and changing the value. This will help you keep the threaded view stuck across the different sorting methods.