I've almost finished this hard sudoku, but I cannot finish it without guessing or making multiple blind steps to see if I'm wrong or not. Even https://www.sudoku-solutions.com/ gives up and says "there is no hint available". I've tried to apply as many solving techniques as possible, but to no avail. Can anyone help?
Solution method that uses value propagation and digit elimination, but not explicit case-by-case analysis:
G1 = E9. (That's because of how they interact with G9.) That digit is not 2 because that would squeeze out digit 2 from the DEF123 square altogether. Therefore it is 8.