Power management on laptop-like devices is a problem for Linux because of lazy manufacturers. ACPI often reports broken values and h/w vendors patch it up using Windows driver overrides, rather than a real fix. Suspend/resume is a delicately choreographed set of steps given to the OS by ACPI so if that's wrong, you'll get awful battery life or worse, crashes. Linux devs will emulate the Windows driver patches but that comes later, if at all.
I mean, hopefully it would work but Lenovo would need to not take the easy way out. They've been slipping, even with their Thinkpads lately.
Yes, but things like that take time. So yeah: Six months after the device is released there will probably be fantastic Linux support. Until then it'll be hit or miss from an "annoying fucking bugs" and "where'd my battery life go?" perspective.
This is why it's always better when a device manufacturer supports Linux right out of the gate. Not only does that give the device vastly more capabilities it also helps Windows by ensuring that the hardware doesn't require all sorts of wacky ACPI workarounds and custom software be developed in order to do things like check the temperature or battery capacity (things that Lenovo has made absurdly proprietary in the past).
I think most people now when looking at portable gaming devices like these want a seamless experience (like with the Steamdeck)
Windows has proven to be problematic with these devices, where when you use the Steamdeck it's pretty much pick up and play. The ROG ally uses Windows + it's own armory crate software and from what I've heard it's been pretty hit or miss