Duolingo NL from EN versions:

Trees:
v0: 2013-11-02  ? (Beta)
v0: 2013-12-23  ? (Beta)
v1: 2014-05-15, ? Skills (? Different lessons)
v2: ?, 123 Skills (123 Different lessons)

Paths:
1.0: 2022-09-10, 123 Skills (123 Different lessons) (79 Units)
1.1: 2023-09-10, 123 Skills (123 Different lessons) (80 Units)
1.2: 2024-05-01, 123 Skills (123 Different Lessons) (140 units)

tree_nl-NL_en_v1_experiment
tree_nl-NL_en_v2_experiment

https://liuch.github.io/duolingo_courses_overview/
https://duolingo.fandom.com/wiki/Course_list
https://duolingodata.com/
https://duolingodata.com/oldtable.html
https://ardslot.com/duolingocrowns.html

Edited by Mat!/Ozone, 2024-05-02.