Open Liberty Microprofile-JWT always returns 401

I'm currently working on implementing JWT authentication on our backend via microprofile jwt (v1.2) on an Open Liberty server (v22.0.7.). The JWT is issued by a keycloak server.

It seems, I am somewhere mistaken though, because all my API calls return '401 Unauthorized' as soon as I add the RolesAllowed Annotation. And according to traces the principal is null.

My Microprofile properties (sensitive information in [ ]):

mp.jwt.verify.publickey.location=[host]/realms/[realm]/protocol/openid-connect/certs
mp.jwt.verify.issuer=[host]/realms/[realm]
mp.jwt.verify.id=myJWT
mp.jwt.verify.userNameAttribute=upn
mp.jwt.verify.audiences=backend

I also tried:

META-INF/micro-profile.properties:

mp.jwt.verify.publickey.location=[host]/realms/[realm]/protocol/openid-connect/certs
mp.jwt.verify.issuer=[host]/realms/[realm]

server.xml:

<mpJwt
id="myJWT"
userNameAttribute="upn"
audiences="backend"
/>

My Resource class:

@Path("/[path]")
@RolesAllowed({ "Authenticated" })
public class MyResource implements MyApi  {
[...]
}

My Application class:

@LoginConfig(authMethod = "MP-JWT")
public class MyApplication extends Application {
  
}

My token payload:

  "exp": 1662994046,
  "iat": 1662986846,
  "jti": "a0a92213-ae77-43fd-b0b8-8cb2f15524b2",
  "iss": "[host]/realms/[realm]",
  "aud": [
    "backend"
  ],
  "sub": "6194ef8a-dbe2-46fb-aa88-64dd61b4c8bc",
  "typ": "Bearer",
  "azp": "frontend",
  "session_state": "6c60affa-b613-49cd-8e8b-a06b16eb8e61",
  "acr": "1",
  "scope": "microprofile-jwt",
  "sid": "6c60affa-b613-49cd-8e8b-a06b16eb8e61",
  "upn": "name",
  "groups": [
    "Authenticated"
  ]
}

I also tried the suggestion in Microprofile JWT responding with 401 all the time to no avail.

My API calls are made like normal, with the added Header:

"Authorization: Bearer [token]"

Finally you can find tracing in this pastebin