It seems that an X-Adapter that can apply SD1.5 assets to SDXL has been released. Personally, I would like to port ComtrolNet poses.

X-Adapter: Adding Universal Compatibility of Plugins for Upgraded Diffusion Model

X-Adapter enable plugins pretrained on old version (e.g. SD1.5) directly work with the upgraded Model (e.g., SDXL) without further retraining.

Github: https://github.com/showlab/X-Adapter