I'm searching for an answer to this possibly as well.
I don't *know* if this would work, but would it be possible to set up two pages: one public with information, possibly a demo, and a donation button, then a private page in "restricted" mode that the creator provides download keys to access when people donate the specified amount, which has the browser-play game?
I know they are called "download" keys, but according to the reference material it says a download key gives "access to a page," unless I'm misunderstanding.
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Using Restricted
Restricted allows only the people you've approved to access your page. Access will let them download files, participate in the community, and use anything else you've enabled for your page. You can give people access by sending them a Download Key that they can attach to their account. If you revoke the key then they'll lose access to the page.
The following option is also available for Restricted:
- Also allow a password to view page — You can provide a password that must be entered by anyone who wants to visit the page. People who already have access for another reason do not need to enter a password. You can also include the password directly in the URL so it’s not required to type it in.
Restricted projects will not show up on itch.io’s browse pages, search results, or profile pages. They will also not be indexed by external search engines.
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Downside to this is creator has to manually fiddle with granting access keys.
I am sure there are reasons why online browser-play isn't allowed, but surely there would be a way - such as allowing the author to specify the "Run Game" button for browser play doesn't appear unless the accessing account has donated/paid a specific amount...