Are there any expert knowledge subscription sites that focus on creators selling premium lessons and audio episodes?

Yes — there are a few “expert knowledge” / creator subscription platforms that are a good fit for selling premium lessons and audio episodes. The best-known ones include:

Creator-focused subscription platforms

• Patreon
  Great for membership tiers, premium audio, lesson series, and gated posts. Works well if you want to bundle lessons + audio + community.

• Substack
  Best known for newsletters, but it also supports paid podcasts/audio and can work for lesson-style premium content. Strong if your audience already likes email-based content.

• Kajabi
  More of an all-in-one knowledge business platform. Good for structured premium lessons, courses, audio, and memberships. More “professional course business” than “creator feed.”

• Podia
  Good for selling digital products, memberships, lessons, and audio files. Simpler than Kajabi, often easier for solo creators.

• Ghost
  If you want a membership site with premium posts and audio, Ghost is strong and more flexible technically. Good for creators who want more control over branding.

• Memberful
  A membership layer you can add to your own site. Good if you already have a website and want gated lessons/audio content.

More niche / relevant depending on format

• Supercast
  Strong for premium podcast subscriptions and private audio feeds.

• Supporting Cast
  Similar to Supercast, focused on paid podcast feeds and premium audio content.

• Uscreen
  Better for video-first education, but can also support memberships and digital content.

If you mean “expert marketplace” sites

If you’re thinking of platforms where experts sell knowledge directly to an audience, also look at:

• Teachable
• Thinkific
• LearnWorlds

These are more course platforms than creator subscription sites, but they’re excellent for premium lessons.

If you want, I can narrow this down by your use case:

1. audio-first creator
2. lesson/course creator
3. newsletter + premium audio
4. own-brand membership site