How to debug Distrobox not being able to open Wayland display?

I am following this [guide on Unix SE](https://unix.stackexchange.com/a/791365/8305) to run Wayland apps as another user. Host Wayland and XWayland applications work fine following the guide, but Distrobox guests in the second user cannot open Wayland display. (Second user Distrobox application does successfully run over XWayland if `$DISPLAY` env var is passed, along side the appropriate permission `xhost +local`)

Pretty sure this I'm running into some edge case. Since it's pretty much a "me" problem, I want to figure it out on my own... That said, I don't know how to get started on troubleshooting whatever's going on here. Any pointer on how to get started?