Why Are My Photos Sorted by Filename Instead of Date?
Your file manager fell back to name order because the dates are useless. Here is the real fix.
Usually because sorting by date has stopped telling you anything, so the name is the only thing left that varies.
After a Takeout export every file carries the same date: the day you unpacked it. Sort by date and the order is arbitrary. So you switch to sorting by name, and now the order depends on whatever your camera called the files, which mixes years together whenever a counter rolled over.
Neither is your library in order. Both are workarounds for the missing dates.
Fix the dates and sorting by date works again everywhere, in every app. If you also want names that read properly, the app can rename each file to its capture date and place: 2019-07-14 Paris.jpg. Then sorting by name and sorting by date give the same answer, which is the point. The first 500 photos are free.