That’s the first thing I thought after going through the linked article. We strongly need some aggregating tool for all events happening around a particular location.
schema.org is used by about a third of web sites to allow them to be self contained but make their information discoverable and reusable in a precise way, and it is the skeleton of the much-promised semantic web. The main factors working against it are Facebook and Amazon, who have enough mass and selfishness to want to be self-contained worlds.
That is the only reasonable way to "decentralize" this data so anyone can use it. Add your recognized sites once (or perhaps have a recurring crawl) and anyone can have their own feed of events, just like RSS. It's just that developers and startups don't like the boring work of following standards, they'd rather build a tool.
[edited to add details about schema.org]
Part of censuring Big Tech should be forcing them to adopt open standards, XMPP, RSS, Microformats, etc.
Of course I guess that's no different than crawling the web. Just saying that even with the data itself you need some serious spam detection to make it useful.
It's only tech events in the US but a fairly exhaustive list.