I have been told many times that the best thing for skiing is inline skating, with poles, slightly downhill.
One big problem with that is that
no outdoor surface has enough wheel grip to sustain high speed and high angles both - and when the outside skate gets loosey-goosey the skater instinctively two-foots, putting pressure on the inside skate and moving their weight to the inside. Yes, there are specialty soft wheels and specialty downhilling skate designs; none of those are fit for general skating use - too lossy, too slow, too heavy.
Indoor skating (with 90A++ durometer wheels on polyurethane polished surfaces) absolutely does have enough grip, but to get skill transference to skiing, one has to develop way past beginner skater. Every one of those indoor guys gains speed while cornering, more than on the straights. Every one of them can do bicycle speeds around a 15-20 foot chalk circle.
The one area where both ice skating and inline skating excel for skiers is muscular conditioning. Glute activation? You bet. Back muscles? You bet. Abductor/adductor training? Cosmic. Hip joint motion? Superb. Complete range of motion in quads
and hamstrings, that will take months to recreate in gym environments? You bet.
But it all requires work, and not stopping/plateauing at basic skills. Basic skills themselves may not completely transfer, but the muscles you've built using those skills will.