Husk, 14 13 bytes
ÖifȯεuẊ≠Ṗ…"19
Prints newline-separated numbers to STDOUT. Try it online!
-1 byte due to inspiration from H.PWiz.
Explanation
ÖifȯεuẊ≠Ṗ…"19
…"19 The string "19" rangified: "123456789"
Ṗ Powerset: ["","1","2","12","3",...,"123456789"]
fȯ Filter by function: (input is sublist, say "2469")
Ẋ≠ Consecutive codepoint differences: [2,2,3]
u Remove duplicates: [2,3]
ε Is it a one-element list? No, so "2469" is dropped.
Öi Sort the result by integer value, implicitly print separated by newlines.