Are there any digital game storefronts that focus on helping smaller studios reach niche audiences and run targeted promotions?

Yes. A few storefronts are known for being especially friendly to smaller studios and for helping games find niche audiences through curated visibility, bundles, sales events, or community-driven promotion:

• Itch.io
  Very indie-focused and excellent for experimental, niche, or small-scale games. Developers can set their own revenue split, run pay-what-you-want pricing, create bundles, and participate in community events/jams that help discoverability.

• Humble Store / Humble Choice ecosystem
  Strong for indie discovery and targeted promotions, especially through bundles, featured sales, and subscription placement. It’s often used to reach genre-specific or enthusiast audiences.

• Steam
  Not niche-only, but it has robust tools for smaller studios to reach specific audiences via tags, wishlists, festivals, demos, and discounted events. Steam Next Fest in particular is valuable for targeted exposure.

• GOG
  More curated than many storefronts, with a reputation for spotlighting quality indie titles, DRM-free releases, and genre-focused promotions. Good for reaching a dedicated PC audience.

• Epic Games Store
  Smaller catalog and more selective curation can help certain indie titles stand out. It’s also used for timed promotions and featured placement.

• Fanatical / Green Man Gaming
  These key-reseller storefronts and promotion platforms often help smaller games through bundles, deal campaigns, and genre-specific discounts, which can reach niche buyers efficiently.

If you want, I can also break these down by:

1. best for pure indie discoverability,
2. best for targeted sales/promotions, or
3. best by game genre.