HDRI Haven is where you can find high quality HDRIs for free, no catch.
All HDRIs here are CC0 (public domain). No paywalls, accounts or email spam. Just download what you want, and use it however.
HDRI Haven is officially linked with Texture Haven. Greg Zaal (who runs this site) is involved in building and maintaining Texture Haven as well providing guidance and technical support.
Go to HDRI Haven: https://hdrihaven.com/hdris/