Logic Masters Deutschland e.V.

Previous Dutch Flat Mate Puzzles
This has been a weekly series since '18 Oct 23'. Here is a spreadsheet link for all the previous puzzles in the series, which also has a few teasers for upcoming constraints/guest setters in the series (subject to change).
This alternative link offers a limited LMD search for Dutch Flat Mates.

Special Thanks
The inspiration for this puzzle is Interval Sums Sudoku by Qodec.
Also a huge shoutout to palpot, who helped me work through a few ideas for this one.

To play the puzzle, please click the image:

Initial Setter Difficulty: 3 / 5

Normal Sudoku rules apply
Place the digits 1-9 so that they do not repeat in any row, column, or 3x3 box.

Dutch Flats
Every 5 in the grid must have a '1' directly above it or a '9' directly below it. It may have both, but it doesn't need both.

Interval Sums
Interval Sums: Let A and B be the two cells nearest an outside clue in the row or column indicated by that clue. Then the outside clue represents the sum of the digits in positions A through B, counted from that outside clue away into the grid.

Visual Rules Example:
In order:
21 is the sum of the digits between positions 3 and 5 (yellow) 4+9+8=21
10 is the sum of the digits between positions 2 and 5 (from the right!) 1+4+3+2=10
32 is the sum of the digits between positions 1 and 7 (yellow) 1+7+2+3+5+6+8=32

Hint to start

The Row 1 clue is a quick pencilmark win, now where is 5 in Box 1, without breaking any clues?