I completed a (rather large) contract to reverse-engineer, and eventually rebuild, a hotel chain's property management system from scratch from 2015-2018. We did it all: keycard integration, booking channel sync, credit cards, group bookings, yield management, front-desk GUI, supply management, taking rooms into/out of service, reservation migration from old system to new...you name it, we probably touched it. Dozens of small lessons about the lodging (and broader hospitality i.e. restaurants, country clubs, bars) business domain.
One thing is that hotel = brand (flag) + real estate + operations. You can remix those things in a lot of different ways, e.g. a single ownership group might have two properties on opposite sides of a street, one Hyatt the other Hilton, and they might look different but share staff, or procurement.
The industry's term for brand -- "flag" -- says a lot about how they view Hilton/Hyatt. They come and go, even if the staff running the property stays the same. The main reason hotels choose to flag vs. stay independent, is access to the chain's booking flow.
One of the more interesting consequences of this setup, is that small, independent hotels, are kind of a shit show in terms of technology. Chains generally require a lot of standardization of their member properties, including what software they run to manage the property. Many properties that don't affiliate with a chain don't have any property management system at all. It's basically 10-20 rooms run directly off the moral equivalent of an Excel sheet at the front desk. And why wouldn't it be--small boutique hotels often gross $1-2 million/year; there isn't budget for expensive enterprise software, or maybe more critically, the people who know how to deploy and operate it.
A significant value-add of Expedia and booking.com, especially with independent properties, is getting the supply (hotel) side of the market organized. Many of these hotels outsource their entire reservation tracking system to a single channel (e.g. booking.com) because trying to keep track of bookings across phone, direct web, Expedia, booking.com, and others, is just too hard without specialist software that requires more IT muscle to deploy than a single non-chain hotel can muster.
I mention this because I go to church every Sunday and was thinking about how much real estate churches have (event halls) that sit unused, and what a schlep it would be -- although good for everyone -- to expose the collective supply of the world's churches, HOAs, park districts, and other nonprofits, to the kind of events you're trying to do. It would indeed be a tremendous pain in the ass to get all the physical access (keys), contract terms, payment systems, availability, etc ironed out, but it's a massively underused class of real estate and many of these organizations could really use the cash.