Twitch is really the least employee vs employer relationship as payment is essentially independent of specific actions preformed by the streamer. It’s not like a streamer is paid to beat a boss, or even play a specific game it’s a question of entertaining people.
IMO it’s the closest to a ‘new economy‘ out there, though sharing roots with earlier real time online performers (porn).
But on that note, a lot of people seem to be ignoring the crucial differences in the transactional relationships between the parties for websites like eBay.
Sellers use eBay to conduct auctions and sell their goods. They have control over inventory, pricing, starting and ending auctions, accepting final bids, etc. eBay as acts the seller's agent and provides services to the seller with respect to transactions similar to how an employee or contractor would. IOW, eBay is acting as a contractor to the seller.
Similarly, for AirBnB, hosts use AirBnB as a marketplace for provider hoteling services. AirBnB is acting as their booking agent and payment collections agent for the host. IOW, AirBnb is acting as a contractor to the host. To the extent that AirBnB itself is paying the hosts (and is not merely passing along money from guests), it isn't for providing hoteling services on AirBnB's behalf, rather it's an incentive for making a property available on the AirBnB marketplace. (I know this because my former employer got paid $$$ to make certain beachside properties it owned available for booking on AirBnB, and these payments were separate from payments we received related to AirBnb-booked stays.)
For Uber/Lyft, the relationship is reversed. The driver is acting as an agent for Uber/Lyft: Uber/Lyft assigns them a ride, and they must provide the ride to get paid. Moreover, in contrast to actual marketplaces, the amount drivers get paid by Uber is not directly tied to the amount charged to the passenger; indeed, driver's generally do not know how much riders actually pay for a trip unless they ask the rider what they're getting charged. This indicates that the transactional relationship for both the driver and the passenger is with Uber, not each other. (Further explanation would dive into principles of contract law, so I leave it to you for further research if you want to go down that path.)
Hotels aren't classified as a service in the US? Or is this going along with the fiction that Airbnb is different from hotels (and not subject to regulations etc) the same way uber isn't a taxi service?
Airbnb: no, because hosts aren't being paid for providing services, they're being paid for providing access to their accommodations. Its a subtle distinction but one that matters legally since it means there isn't a compensation-for-work arrangement. (A host can choose to voluntarily go above and beyond, but that's not required or expected.)
Amazon Marketplace and eBay: No. The Amazon marketplace acts like a real marketplace, so sellers transact with the buyers for AM purchases and Amazon acts as an agent of the seller in that transaction. Sellers determine what they sell on Amazon, how much they charge for the products they sell, and are largely responsible for acquiring sales traffic on their own. Sellers independently acquire and own the inventory they sell on Amazon, and can sell on their own websites or on competitors' websites. Crucially, Amazon isn't paying AM sellers for their labors in selling products. They only receive payment for goods actually sold, meaning again, there is no compensation-for-work arrangement.
Also, for Amazon and eBay: AB5 carves out exceptions for direct sales, in this context defined as any sales not made through a retail store, so direct sales salespersons may continue to be treated as contractors or employees as the business so chooses.
Twitch: Possibly! Twitch and streamers are in the business of streaming live video. Streamers are usually exclusive to a particular streaming service. And generally, except for the biggest streamers, they are unable to set or negotiate their own rates for streaming.
BUT...Twitch doesn't actually pay streamers for streaming; most of them do it for free. When it does pay streamers, it pays them commissions and marketing fees for any ad revenue, sales of digital products, or subscriptions tied to their channels (even if not actually arising from streaming), and marketing services and commission-based arrangements are largely excluded from AB5. And generally, for the bigger streamers, it pays them through personal companies so that AB5 does not apply (since AB5 does not apply to contracts between two legal entities).