Usually in the German health sector the use of existing standards is only there for marking off a checklist I have the feeling. In practice things are so heavily adapted that you often cannot use existing libraries.
6 different sets of definitions by 5 different regulating bodies, with the organizing company Gematik GmbH owned by 9 different stakeholders: https://www.gematik.de/ueber-uns/struktur
Just look at the authentication of the E-Rezept (electronic prescription) service: https://github.com/gematik/api-erp/blob/master/docs/authenti... This is supposed to be standard OpenID.
I fully expect the matrix protocol to suffer the same treatment under the hand of the Gematik.
If you want to know how things end up such a chaos take a look at the definitions of the payload data: https://github.com/gematik/api-erp/blob/master/docs/erp_fhir...
6 different sets of definitions by 5 different regulating bodies, with the organizing company Gematik GmbH owned by 9 different stakeholders: https://www.gematik.de/ueber-uns/struktur