I think that's not an unreasonable point, but, well:

1. I try not to tell people what to do with their free time. While you may think it's "bizarre", this use of their time has value to them, not only in the hopeful end result (fully-functional Linux on ARM Macs), but also in the satisfaction of the technical challenge, bragging rights, and general reputation. I'm sure there are some people who might look at what you do with your spare time and think you're "wasting" it sometimes. But that's in the eye of the beholder, and at any rate, that's your prerogative, as this is theirs.

2. I used to run Linux on Mac laptops (gave up around 2016 or so, tried again in 2018, gave up again shortly after), and I get the appeal: the hardware is really nice. And by all accounts, the ARM Macs are even nicer than the Intel Macs. Sure, they're not perfect (lack of upgradeability/repairability, etc.), but running Linux on them can be great, if the hardware support is there. "I like this hardware and I want to run Linux on/with it, so I'll figure it out myself" seems like a perfectly reasonable thing to do. Many of the drivers in the Linux kernel for various bits of hardware only exist because someone adopted this attitude.

I also just think your premise is a bit flawed:

> open source developers go so far to contribute to a closed source proprietary ecosystem

This is a little bit of a weird statement, because these developers aren't doing that. The "closed source proprietary ecosystem" is macOS and its app store. The hardware itself is more or less just as open (or closed) as most non-Apple hardware. I mean, I can't rewrite the BIOS in my Framework Laptop, nor can I make heads or tails of any of the binary firmware blobs Linux loads into the WiFi chipset, graphics chipset, etc. Apple's hardware is undocumented, certainly, but that's pretty common when it comes to Linux hardware support.

> but they at times actually intentionally impede their work

Do they, though? From what I've read of the Asahi project's progress, they didn't run into cases where Apple intentionally tried to make things harder on them. Sure, some things were harder, but I don't think we can ascribe a malicious motive to Apple. The most likely explanation is that they just decided to design things in a particular way because they felt it would be best for their own purposes, and didn't really care to think about anything else.

They could have decided to actively cryptographically lock down the boot process to prohibit other OSes from running, but they didn't do that.

> That is a lot of time and effort of someone doing something for free that the manufacturer should be paying them to do and assist with.

Why "should" they? All hardware manufacturers decide what software to write, and what platforms to support. If they don't think the cost of writing and supporting drivers for Linux is worth what they'll get in return, they'll make the logical choice to just... not do that. We've seen plenty of vendors over the 30-odd-year lifetime of Linux do that math and decide Linux support wasn't worth it to them. It's a shame, but I don't think it's fair to come down on them hard for that. Certainly some vendors (nvidia comes to mind) have been actively hostile toward the Linux community at times, but I don't think we can say the same of Apple.