What temperature does that result in on your RX580? Without dGPU fans running I assume.
Please dump the result of this when idle. Then I can compare.
ioreg -l | grep PerformanceStatistics | cut -d '{' -f 2 | tr '|' ',' | tr -d '}' | tr ',' '\n' | grep -i 'Temp\|Fan\|%\|(W)\|Hz|state|(V)|volt|vddc'
Mine says
"Device Utilization %"=0
"Fan Speed(%)"=13
"GPU Activity(%)"=0
"Fan Speed(RPM)"=577
"Temperature(C)"=51
"Total Power(W)"=107
"Device Utilization %"=1
"Fan Speed(%)"=13
"GPU Activity(%)"=0
"Fan Speed(RPM)"=577
"Temperature(C)"=51
"Total Power(W)"=107
"Device Utilization % at cur p-state"=0
"Device Unit 0 Utilization %"=0
"Device Unit 1 Utilization %"=0
"Device Unit 2 Utilization %"=0
"Device Unit 3 Utilization %"=0
"Device Utilization %"=0
Some say Power is not reported right. I don't know. The temperature does seem likely though as it fairly hot at the heat pipes close dPGU - whereas the CPU cooler seems a lot cooler reporting 32 degrees at heatsink.
I thought the RX580 (and variants like the Nitro+) were natively supported and wouldn't require any manual setup like framebuffer patching. I'm using WEG and lilu on a vanilla install (latest os, clover, kext and drivers). OS reports RX 580 just fine, and no probs using it besides the power management not being great. Would love if some fix could make dGPU power management work better, so any tip is highly appreciated.