Interesting, gotta check out Flickboard.
Btw, long-press for 0-9 can be enabled in Thumb Key with YAML like so:
Code
ENThumbKeySymbols:
main:
key0_0: { longPress: { text: "1" } }
key0_1: { longPress: { text: "2" } }
key0_2: { longPress: { text: "3" } }
key1_0: { longPress: { text: "4" } }
key1_1: { longPress: { text: "5" } }
key1_2: { longPress: { text: "6" } }
key2_0: { longPress: { text: "7" } }
key2_1: { longPress: { text: "8" } }
key2_2: { longPress: { text: "9" } }
key3_0: { longPress: { text: "0" } }
shifted:
key0_0: { longPress: { text: "1" } }
key0_1: { longPress: { text: "2" } }
key0_2: { longPress: { text: "3" } }
key1_0: { longPress: { text: "4" } }
key1_1: { longPress: { text: "5" } }
key1_2: { longPress: { text: "6" } }
key2_0: { longPress: { text: "7" } }
key2_1: { longPress: { text: "8" } }
key2_2: { longPress: { text: "9" } }
key3_0: { longPress: { text: "0" } }