This is probably the crux for a bunch of people. One thing being on x86 did bring was extra flexibility by being on commodity CPUs everyone was using. For folks who were using a Mac because it was Intel+Apple, going to ARM is going to be rough. Those of us who were users in the PPC days had a bit of forewarning that this hurdle was coming. That said, in the long term, I don’t think this is going to be nearly as bad as the PPC days.
There were at least plenty of PowerPC variant versions of Linux that ran on PowerPC Macs. Hell, Yellow Dog was geared for PowerPC Mac users. That's not to say that there aren't a slew of people working on Apple Silicon native Linux versions. But I think, especially given that this isn't just an ARM64 SoC, but a HEAVILY customized SoC is going to make things a lot more difficult outside of mere virtualization.
Microsoft DOES have ARM64 versions of Windows Server, and you, as a customer, are able to use it in Azure, but they do not have it available standalone for use in one's own datacenter, one's own private cloud, on AWS, or on one's own ARM64-based server. It's worse than what they have with Windows 10 for ARM64 currently.When it comes to OS support, it’s a chicken/egg problem. Hardware vendors are going to be slow to adopt ARM hardware if the OS isn’t there, and the OS vendors are going to be slow if the hardware isn’t there. That said, at least on the Linux side, things look promising. A lot of the heavy lifting is done at this point, and Debian/Ubuntu are supporting ARM64 as an official release. This should make it easier for other distros to catch up.
Windows though? That’s entirely on Microsoft’s plate at this point. They have always played things conservatively when it comes to Windows in a lot of ways, but they risk ceding the server space even more to Linux if ARM64 in the data center keeps making inroads. If the rumors that they are working on in-house ARM designs for the datacenter are true, then it’s extremely likely they are working on the changes to WoA to match. Question is more if they are going to keep with OEM-only licensing going forward here.
I still maintain that Microsoft cares about Windows 10 for ARM64 and that Apple Silicon Macs represent a massive opportunity for Microsoft to sell OEMs on the potential of the platform (as even with weaker qualcomm SoC's, native ARM64 code does run well on ARM64-based Windows 10 computers. They wouldn't even have to modify their "it can only be licensed for OEMs" THAT much, especially if they collaborate with Apple on a Mac App Store friendly installer (that would effectively perform the functions that the Intel Mac Boot Camp Assistant and subsequent Windows Support software [drivers] package has done, albeit even more streamlined).