You can do the Hill Sprints in a boot packed track too. Your tempo will be slower than running so to make them have a good strength/power training effect, wear a pack with a decent amount of weight, say 20% of BW. That’ll be super sport specific. Use the same format.
You can do sprints in skimo gear but they’ll be more of a speed workout to teach your legs to turn over. But they can be good for coordination. So if on skis try a mix of short speeds and boot packing.
If none of this works then resort to running.