Are you planning to go 1x, 2x, or 3x?
If 1x, and it can cost a bit more, you can use any 11-speed STI paired with a 1x GRX derailleur and an 11-42 cassette.
2x GRX with an 11-40 cassette and whatever double up front is also supposed to work.
@Tijs started
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Are you planning to go 1x, 2x, or 3x?
If 1x, and it can cost a bit more, you can use any 11-speed STI paired with a 1x GRX derailleur and an 11-42 cassette.
2x GRX with an 11-40 cassette and whatever double up front is also supposed to work.