It's silly to think Apple buying Buddybuild is to discourage development for other platforms for the reason you stated, there are plenty of competitors to both TestFlight and Buddybuild. They bought these two companies because they want to enhance their own developer tools.

Yeah, I might have worded that poorly - buying Buddybuild almost certanly wasn't to interfere with Android development.

Immediately killing all Android related functionality is to discourage that development though.

I don't believe that at all. The obvious reason why they discontinued Android support is because Apple isn't interested in continuing the existing B2B business. They're interested in the technology and the team and they're likely to integrate it into their own developer tools and offer them for free.

Why would Apple invest resources into making developer tools for other platforms? What's the real upside if Buddybuild continued as is and they tried to scale it up? Hundreds of millions in revenue per year? That's a drop in the bucket. Buddybuild's value is strategic, not because it was going to make a financial difference to Apple.

Surely Apple are throwing away a lot of the value of what they just bought; does profiting from that harm their own developer tools. IMO that seems almost impossible, the only harm is to protect their eco-system from competition; ergo the reason to stop supporting other eco-systems is to harm the competition?

Couldn't they fork the project, keep everything but the name for themselves and set a single guy on maintenance; wouldn't that enhance their own developer tools just as much?

I'm an Android fan/Apple hater but I could never recommend anything other than going iOS first for any business interesting in maximizing profit. I actually like to push react native just so clients won't completely ignore Android when see the cost of porting. But really, really I will push PWAs over apps whenever they are suitable.