VLC 3.0.0-rc2 and Chromecast tls error

[Floris]

Maybe I'm missing something very simple, but I'm unable to cast a video  
with vlc to the chromecast due to a gnutls error:
...
[00007f6c20000980] main art finder debug: no art finder modules matched
[00007f6c28003290] gnutls tls client debug: loaded 149 trusted CAs from  
system
[00007f6c28003290] main tls client debug: using tls client module "gnutls"
[00007f6c28003290] main tls client debug: resolving 192.168.1.14 ...
[000055630bb401c0] qt interface debug: IM: Setting an input
[00007f6c28003290] gnutls tls client debug: TLS handshake: Resource  
temporarily unavailable, try again.
[00007f6c28003290] gnutls tls client debug: TLS handshake: Success.
[00007f6c28003290] gnutls tls client debug:  - safe renegotiation  
(RFC5746) enabled
[00007f6c28003290] gnutls tls client debug:  - extended master secret  
(RFC7627) enabled
[00007f6c28003290] gnutls tls client debug:  - false start (RFC7918)  
enabled
[00007f6c28003290] gnutls tls client error: Certificate verification  
failure: The certificate is NOT trusted. The certificate issuer is  
unknown. The certificate chain uses insecure algorithm. The name in the  
certificate does not match the expected.
[00007f6c28003290] main tls client error: TLS session handshake error
[00007f6c28003290] main tls client error: connection error: Resource  
temporarily unavailable
[00007f6c28000f90] stream_out_chromecast stream out error: cannot load the  
Chromecast controller (Failed to create client session)
[00007f6c28000f90] main stream out debug: no sout stream modules matched
[00007f6c28000f90] main stream out debug: destroying chain... (name=(null))
[00007f6c28000f90] main stream out debug: destroying chain done
[00007f6c28000c10] main stream output error: stream chain failed for  
`chromecast{ip=192.168.1.14,port=8009}'
[00007f6c400009e0] main input error: cannot start stream output instance,  
aborting
[000055630bafc1a0] main playlist debug: dead input
[000055630bafc1a0] main playlist debug: changing item without a request  
(current 0/1)
[000055630bafc1a0] main playlist debug: nothing to play
[000055630bb401c0] qt interface debug: IM: Deleting the input
QObject: Cannot create children for a parent that is in a different thread.
...

Apparently, on a windows machine you get a "trust this certificate" pop-up  
window and you are able to import the chromecast certificate. In Debian  
there isn't such window. How to accept the chromecast certificate?

(Please also reply to me, because I am not subscribed to this list)

Floris