Dart

I’m glad I took the time to read the directions very carefully before starting coding :-)

Top Tip: the ranking of hands relies on the fact that if you count instances of each face and sort the resulting list from high to low, you get an exact correspondence with the order of the hand types as defined, so no need for a bunch of if/thens, just

  var type = Multiset.from(hand).counts.sorted(descending).join('');

Otherwise it should all be pretty self-explanatory apart from where I chose to map card rank to hex digits in order to facilitate sorting, so ‘b’ means ‘J’!

int descending(T a, T b) => b.compareTo(a);
var cToH = "  23456789TJQKA"; // used to map card rank to hex for sorting.

handType(List hand, {wildcard = false}) {
  var type = Multiset.from(hand).counts.sorted(descending).join('');
  var i = hand.indexOf('b');
  return (!wildcard || i == -1)
      ? type
      : '23456789acde'
          .split('')
          .map((e) => handType(hand.toList()..[i] = e, wildcard: wildcard))
          .fold(type, (s, t) => s.compareTo(t) >= 0 ? s : t);
}

solve(List lines, {wildcard = false}) => lines
    .map((e) {
      var l = e.split(' ');
      var hand =
          l.first.split('').map((e) => cToH.indexOf(e).toRadixString(16));
      var type = handType(hand.toList(), wildcard: wildcard);
      if (wildcard) hand = hand.map((e) => e == 'b' ? '0' : e);
      return (hand.join(), type, int.parse(l.last));
    })
    .sorted((a, b) {
      var c = a.$2.compareTo(b.$2);
      return (c == 0) ? a.$1.compareTo(b.$1) : c;
    })
    .indexed(offset: 1)
    .map((e) => e.value.$3 * e.index)
    .sum;

part1(List lines) => solve(lines);

part2(List lines) => solve(lines, wildcard: true);