...in exchange for knowing who you are. (If they couldn't de-dup you via some kind of identity verification, they wouldn't be able to offer a free promo, as some asshole could then just come and generate a million free accounts and lash them together to run a botnet/crypto-mining-farm/etc on.)

I believe the GP's question is "is there any public-web hosting platform that I can use entirely anonymously; where they allow me to sign up using a VPN; and where I don't ever have to pass them anything / sign in through anything / link anything that could be linked back to my identity?"

And I believe the answer to that question is "no."

(Well, okay, if you're fine with a static website, you could pin your data using FileCoin, and then set a domain up as a DNSLink pointer to [an IPFS gateway for] the relevant IPFS URN. That's how https://docs.ipfs.io works. But that's not quite what "web hosting" means to most people.)

The moment a service allows anonymous signup it inevitably gets abused the shit out of itself for spam, botnet C&C, DoS attacks and worse.

This is why I don't see how services like Mullvad can stay afloat forever.

You still have to pay for bandwidth. Free tier provides only 1Gb egress.