Does paying the cost to activate a cycling ability count as discarding for cards that care about discarding?

Cycling is an activated ability with a cost that includes discarding the card itself. When you pay that cost, you are genuinely discarding the card — it moves from your hand to the graveyard as a cost, not as an effect. This means it is a real discard event that any card watching for discards will see.

According to CR 702.29a, cycling is an activated ability that reads '[Cost], Discard this card: Draw a card.' The discard is explicitly part of the activation cost (CR 117.1). Any replacement effect or triggered ability that cares about discarding a card — such as Obstinate Baloth's triggered ability or Raven's Crime's targeting restriction — will apply normally.

CR 400.5 confirms that an object that moves from the hand to the graveyard due to a cost is considered discarded. The game makes no distinction between discarding as a cost versus discarding as an effect for the purpose of 'whenever you discard' or 'if a card was discarded' triggers and replacements.

Example: You control Surly Badgersaur, which triggers whenever you discard a card. You activate the cycling ability of Secluded Steppe by paying {1} and discarding it. Surly Badgersaur's triggered ability sees that discard and triggers, letting you put a +1/+1 counter on it (assuming a land was discarded).

One nuance: if a replacement effect would change or prevent the discard (e.g., Containment Priest-style effects are unrelated, but something like Teferi's Puzzle Box doesn't apply here), that replacement would apply to the cycling discard just as it would any other. The cycling ability's cost must still be paid, so if the discard is somehow replaced, you must still satisfy the cost rules under CR 117.1.