Hey there!
I tried different scenarios with RPR 2.0.52, i rendered instance objects, hair strands, collections, higher and lower amount of instances. While everything works fine, when rendering on either of my both GPUs, Blender crashes after the first few bounces, when i use both GPUs for computing.
RYZEN 1700X
ASUS VEGA 64
MSI GTX 980
BLENDER 2.80
RPR 2.0.52
WIN 10 PRO
Great renders you've been posting on Twitter BTW.
Could you post a test file that crashes your multi GPU setup so other users can test it on different GPU combinations?
I've found that hair, when rendered on two GPUs, comes out 50% of object with hair, 50% of object without hair but it doesn't actually crash. On single GPUs the entire object will have 100% hair
Other particle systems e.g. ones using collections as instance objects work fine on two GPUs for me. It is only Hair that was really very funky.
This is on macOS with Metal (therefore AMD GPUs only).