Greg Zaal writes:
Just noticed today that there are now over 300 HDRIs on hdrihaven.com :)
Thanks to continued and amazingly consistent support from Patrons, there are now a handful of us publishing high quality HDRIs twice every week.
You can see (and download) them here - there are no silly email forms, account systems, paywalls, or even watermarks. Everything is free and public domain, and can be downloaded instantly at full resolution - all thanks to support by donations on Patreon.
Since it's been a while since my last update, I've written a bit more about the state of things and potential plans for the future here.