Depends what you're looking for.

• Deep Rock Galactic is my most common recommendation. Dwarves, mining, space bugs. Devs care a lot about the community and community input.

• Elite Dangerous is great if you want an excellent space flight sim (Frontier isn't exactly indie, but the Elite devs operate like one).

• Warframe is fun and has the absolute best, non-predatory F2P model.

• Lost Ruins, Batbarbarian, Aquaria, and Hollow Knight are excellent Metroidvanias.

• Ori and the Blind Forest is technically a Metroidvania, but it's a beautiful experience, from the art, to the story, to the music.

• Yoko Island Express is a pinball platformer. Yes, you read that correctly.

• Blasphemous is a 2D Souls-like.

• Hades, RAD, and Mana Spark are great rogue-lites.

You could spend hundreds if not thousands of hours on the first three alone.