3 fairly up to date authoritative sources come to mind

• duden.de
• Wiktionary ¹
• Owid.de

For instance the entry for Flugscham ° is referencing the other two.

Regarding downloading corpora or API I dunno. You have to check there.

At least the OWID is offering a corpora search.

°) shame of flying (due to the environmental impact of aviation)

¹) OK probably rather open than authoritative