They accept written/scanned proof of identity signed by a municipal office (german here). Basically, show your ID to an official and haven them sign a paper to proof your identity. Also, a friend told me, a LinkedIn Support Member may neither have capacity nor skill to validate a foreign documents authenticity.

Awesome stuff, especially for off-grid comms. Have a look at https://meshcore.io/ and https://lilygo.cc/products/t-deck while you’re at it.