Context: up-to-date, using amdgpu firmware from the linux-firmware git, tested both kernels 6.7.9 (from unstable/sid) and 6.6.15. Xfce 4.18. power-profiles-daemon 0.20 on power-saver.
/sys/class/drm/card1/device/power/runtime_status is forever at active, even with Xorg not running, as well as during ‘rescue mode’. nvtop reports no dGPU activity. Tried telling lm-sensors to ignore the dGPU [1] which did drop the idle power usage I was seeing by roughly half but didn’t let the dGPU suspend. However, it did lead to things taking a couple seconds to load when they did use the dGPU (tested with vkcube and glxgears) and waiting for the 5s timeout, so perhaps this is just an issue with the amdgpu driver in these kernels not reporting power state changes? I don’t currently have an easy way of testing 6.8.x or newer 6.7.x to verify.
[1] Suggested here by motsky80