Lighttpd and subpath: categories and tags not working

[Ixtalo]

Hello,

when I'm using the grav-skeleton-knowledge-base on latest Grav with provided webserver-configs/lighttpd.conf the "Taxonomies" page is always shown instead of the selected Category/Tag, i.e., not showing the articles.

Situation:

• Raspi
• Lighttpd
• Grav, grav-skeleton-knowledge-base
• using webserver-configs/lighttpd.conf with subpath grav_path (Grav not in root)

Problem:
http://localhost:8008/grav_path/taxonomy?name=category&val=Topic%203 does not show "Topic 2" page (with Topic2-articles), but just "Taxonomies" page without any articles/items.

I did not find anything related to this problem at Grav-Github-issues neither on the forum.
It only does not work with lighttpd. Starting it via php system/router.php does work fine (no subpath then).

Any ideas?
Perhaps a problem with subpath/subdir?

To reproduce:

1. grab Dockerfile docker-lighttpd-grav-skeleton-knowledge-base from https://gist.github.com/Ixtalo/06fa139fe33518aa0c105d77e9c40f6a
2. docker build -t grav .
3. docker run --rm -ti --name grav -p 8008:80 grav
4. open http://localhost:8008/grav_path/taxonomy?name=category&val=Topic%203