Normal Sudoku rules: Each row, column and 3x3 box must contain the digits 1-9 once only.
Perimeter sum: The digits around the perimeter of the grid (Row 1, Row 9, Column 1 and Column 9) sum to 171.
Normal Knight's move: Cells that are a chess Knight's move apart from each other cannot contain the same digit.
Normal Arrows: Digits along arrows must sum to the total in the their white circle.
Normal Thermometers: Digits along a solid grey line must increase from the bulb (circle) end of the line.
Puzzle link: https://f-puzzles.com/?id=y3bfw5ek
Easier version: If you'd like an easier version of this puzzle, change the id in the f-puzzle URL to yyqlesuc. The break in is unchanged (I think) and hence still quite difficult, but the remainder of the solve is facilitated by some additional arrow clues. I haven't thoroughly tested it for difficulty, but it should at least be a little easier.
Solution video: Watch me walk through the break in. Video.
Lösungscode: Row 3