I do not know. My search have not fundamentally changed in years, probably 15 years.

Were you using the quick filter (ctrl+shift+K) and it is now not visible perhaps. The keystrokes will make it visible even if it is not visible in the copy of Thunderbird when you press the keys.

Thanks.

My issue is with the display of what the search finds; way too much stuff for me. I want concise results as in prior versions along with search = find.

Which kind of search results display do you miss ? The one provided by the add-on "Search as list" https://addons.thunderbird.net/en-US/thunderbird/addon/search-as-list/ until Thunderbird 60?