The Interloper: Can You Find the Digit that Doesn't Belong in this Sudoku?

Today's Puzzle:

Another excellent puzzle with a bigger mystery on what the title means. My guess is this is about finding which number does not belong on the region sum lines. What's your guess?

Link to Play Along:

The Interloper by 99%Sneaky https://tinyurl.com/SudokuSleuthTheInterloper

Rules:

Normal sudoku rules apply.

Digits along thermometers strictly increase from the bulb end.

Adjacent digits along thin green lines must have a difference of at least five.

Thick box borders divide thick blue lines into segments with equal sums.

The digits separated by the black dot are in a 1:2 ratio, i.e. one is double the other.