Hey Everyone,
I like many am still experiencing the external monitor wake bug (where the external monitor comes on, but the connection is lost and goes back into standby) when my m1 max 14" MBP wakes up from sleep (using a Cable Matters usb-c to hdmi w/ PD adapter). After updating to Sonoma 14.1.1, the issue still remains. The only workaround I've found that doesn't involve disconnecting and reconnecting the adapter, or turning the monitor on prior to waking the mac (or any other workaround) is to use "hibernatemode 25". This is acheived using "sudo pmset -c hibernatemode 25". The -c is to apply the setting only to AC power, but -a will apply to both battery and charger (or just battery would be -b).
"hibernatemode 25" is where the memory is stored to a sleep image and the memory is powered down (unlike with hibernatemode 3 where the memory stays powered). This may also power down USB ports, as it is essentially shutting down the mac.
The only annoyances are that it takes longer to wake from sleep (as it has to restore memory from the sleep image) and you HAVE to input your password after it wakes even after disabling requiring password after waking from sleep.
Since enabling this, my MBP has successfully woken my monitor and established a connection without issue, even after sleeping over night.
Every other pmset combination I've tried doesn't work and results in the same troublesome wake behavior. I also observed in console that when the MBP fails to establish a connection with the external monitor, there's a windowserver log that says "failed to get EDID 0x000XX" or something to that effect.
Hopefully Apple will address the external monitor issue as it appears to be a well-known issue, however, I'm not holding my breath.
For reference, my setup is a 14" MBP m1 max 32c and a Samsung Neo G9 QLED (mini-LED). I am using 144hz at 5120x1440.
Best of luck to you all!
