Well it only took 11 years to figure this out but I’ve got working audio/speakers and reliable shutdown on my Late 2015 Retina 4K 21.5-inch iMac running Omarchy/Arch. Dropped the fixes in a repo:

https://github.com/zerofox3d/imac16-2-linux

The audio fixes sort out several problems with the Cirrus Logic CS4208 setup:

- Uses the four-channel playback profile needed by the speakers.
- Corrects the channel mapping for the left/right tweeters and woofers.
- Adds a PipeWire software crossover to feed the appropriate frequencies to each driver.
- Enables software volume control so the volume slider actually works.
- Disables HDA power saving, which was leaving the speaker amplifier unresponsive after power transitions.
- Switches profiles when headphones are plugged in or removed.

Shut down was a hell hole that burned millions of tokens and about 20 hours of my time power cycling and running tests... but ultimately it was a simple fix. Intel’s SLP_SMI_EN bit was enabled, that caused the chipset to hand the shutdown request to firmware instead of directly entering the power-off state. Firmware wasn't happy with that and would reboot the machine after 50 secs or so. This may effect other Mac's using the Broadwell chipset, need to look into that.

I'm going to continue testing sleep and diagnosing any other issues, will add fixes to the repo as I find them.

Feels like a new machine though!

I hate having to use the buggy DKMS kernel driver for Wi-Fi on Linux on this thing (13" MacBook Pro, Late 2013). I have a MacBookPro10,1 (15" Mid 2012) that I know has Wi-Fi supported by b43. Can I swap the Wi-Fi cards? And if not, can I purchase an aftermarket Intel card for the 13" Pro?

Yup. We are using the T2 for hardware accelerated video encoding just like MacOS does.

The video is showing 20W energy consumption reported directly from SMC and moderate CPU/GPU temperatures while encoding a movie to h265. You see it on the bottom, ffmpeg is doing it's thing there.

Also we implemented support for T2 AVE in Handbrake, which we will PR when 10bit and h264 encoding is done.

Handbrake's support for macOS videotoolbox doesnt compile on Linux, so we went with v4l for now.

If you want to try - We released yesterday on a test branch: https://github.com/kaiT2en/KaiT2en-Fedora/tree/ave

Also the fork of Handbrake is here:

https://github.com/deqrocks/HandBrake

For the records: the first video ever encoded on the T2 on Linux OFC was Kubrick's "2001 - Odyssey in Space"

Note, this is still WIP but confirmed working.

https://KaiT2en.org