Logic Masters Deutschland e.V.

Having done sandwich variants before, I wondered if sandwich rules could be applied to an irregular sudoku.
The only way I found to do this do this was to have regions all one cell wide paths and it proved quite tricky to create an irregular sudoku with 9 regions with both that characteristic, and that didn't end in ambiguity for the crust locations, and I'm quite happy with the below result.
As it needed more information to solve completely, and I didn't want to just add normal row/column sandwich clues, I created "outer" sandwich clues using different digits for those sandwich crusts, and, between both sandwiches, the grid can be completed.
The digits for the outer sandwich can only be deduced once the inner crusts have been completed, so you could call this an "onion" sandwich :)
Hope you enjoy.

• Standard Irregular Sudoku rules apply - each row, column and specified regions must contain all the digits from 1 to 9 once only.
• Digits on the thermometers must increase from the bulb end to the flat end.
• Inner Sandwich
  • Each region should be treated as a one cell wide path/line
  • Numbers inside the grid (in black) at the ends of each region refer to the sum of the digits sandwiched between the digits 1 and 9 for that region. (The sums are given at both ends simply for readability/ease of reference)
• Outer Sandwich
  • Numbers outside the grid (in green) refer to the sum of the digits sandwiched between the digits X and Y for that row/column (The colour has no relevance, and is just meant as a a visual reminder that the outer sandwich clues are for a different sandwich)
  • X and Y are not given, and need to be discovered:
    • X is the row number that the digit 1 appears in the first column
    • Y is the row number that the digit 9 appears in the ninth column
  • In the example below, if the digits were found as follows, X would be 4, and Y would be 1, and therefore the outer clues would refer to the sum of the digits sandwiched between "1" and "4"

link to solve this online is available via Penpa at https://tinyurl.com/y9vt76zs