I figured out that plex has some issues reading the cert.
After applying a fix mentioned here one error message about enveloping was gone.
But now I still have the following error message even in DEBUG and I won’t get any more infos:
Sep 27, 2023 17:32:03.319 [140503353031312] DEBUG - [CERT] Subject name is /CN=*.2fe2a31f04994a16946eb36b9bc676bd.plex.direct
Sep 27, 2023 17:32:03.319 [140503353031312] DEBUG - [CERT] Installed certificate with fingerprint aa:ea:8a:bd:88:55:cb:83:78:fb:3e:17:76:e0:b7:2e:a6:e6:a4:96.
Sep 27, 2023 17:32:03.319 [140503353031312] DEBUG - [CERT/OCSP] Stapling requests will be made to 'http://r3.o.lencr.org/'.
Sep 27, 2023 17:32:03.320 [140503353031312] INFO - [CERT/OCSP] Successfully retrieved response from cache.
Sep 27, 2023 17:32:03.320 [140503353031312] ERROR - [CERT] Found a user-provided certificate, but couldn't install it.
Priv key algorithm:

Pub key algorithm:

Signature:

Any idea what this might be about?