On European beech.
As mentioned in my comment below, I collected this nymph at the same site I documented a cave cockroach in July 2021. https://www.inaturalist.org/observations/81462214
I had been meaning to come back since then but finally got around to it to check for more. I collected this one and have it alive right now at home. There were plenty of surinam cockroaches around it but this one looked different and my photos appear to match the one I documented in 2021 and other photos online.
Photos showing location: https://flic.kr/p/2opyDXJ
Related observations of organisms under same rock and nearby rocks:
https://www.inaturalist.org/observations?on=2023-03-27&place_id=any&user_id=joemdo