imac27 linux rtcwake

Basically, what I think you are looking for is low-level hardware documentation that Apple has not published, and that others have not figured out yet.

macOS users are never going to be messing around at this low level of the system, and Apple considers the machine “obsolete.” So even though I don’t think it would hurt Apple to release the information, I don’t think they are likely to spend engineering time to gather and publish it for you.

If you want to make this work, you and/or other Linux users are going to have to figure it out.

I suggest you ask in a user group for the Distro you installed.

Suit yourself, but you're trying to install Linux and it just seems to me a concentrated group of Linux users might have what you need from their intense usage of the Distro more so that a concentrated group of Apple users. The subject here is how Linux operates within the AppleS environment after all..

The Linux people are responsible for making their product work with Apple, not the other way around.

Given the nature of your problem, and the fact only I have responded, you need to consider that as this is community of volunteers the people with the expertise you need have not "checked in" as it were ... they may never do so.

But, good luck. Maybe a Linux user with the skills you need will come along by and by.

Re: “The Linux people are responsible for making their product work with Apple, not the other way around.”

Actually, I doubt if there are any Linux people offering up Linux as a commercial product to be run on old Mac hardware. They might try to help the OP out of the goodness of their hearts, or because some of them are also interested in getting use out of old Mac hardware.

But I don’t think they have the obligation that, say, Adobe or Microsoft would have after taking your money for something advertised as being compatible with a particular Mac platform.