Logic Masters Deutschland e.V.

Special Thanks
I believe Matt Tressel (MSDOS) is the inventor of Tentropy lines, but ChinStrap is also a strong ambassador for the constraint.
Also a small nod to Qodec, who last week released the sudoku variant puzzle Terrace, which uses Dutch Flat Mates really well.

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.

To play the puzzle, please click the image:

Initial Setter Difficulty: 2.5 / 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.

Tentropy Lines
Every set of 4 adjacent digits on a peach line must contain a digit from each of the X-pair (ten-pair) subsets of {1,9}, {2,8}, {3,7}, and {4,6}. A 5 may not appear on a tentropy line. Digits on a line may repeat if allowed by other rules.

Column Indexing
Selected column 5 digits (from row 4 to row 9) indicate the column in which the digit 5 appears in that row. Example - if R9C5 is 8, then 5 is indexed into R9C8.

Hint to start

You might benefit from colouring the ten pairs, some options for 19 make 5 sad. Even though the top 3 row don't directly index the 5, they still have an impact on the options for 5s.

Guests Setters
Over the next 2 weeks, we have guest setters, including 2 new setters to the series!
First up, we have a collab from returning guest sujoyku and, welcome to the series, mellowrobinson with their wonderful Killer Lines constraint, as seen in this puzzle: Price Tags.

Then we welcome another new guest to the series, and a puzzle from juggler, probably the most inventive setter in the community, with something suitably imaginative.