Unable to get self signed ssl webserver certificate working on debian

I’ve used this selfsigned ssl certificate for a while now, but since the last mono update on my headless debian duplicati host https does not seem to work anymore.

I use these options when running duplicati :

DAEMON_OPTS="–webservice-port=8200 --webservice-interface=10.0.1.31 --webservice-sslcertificatefile=/etc/ssl/certs/duplicati.p12 --webservice-password=foobar"

error messages seems to be flooding the syslog on my host :

May 5 23:35:29 duplicati duplicati-server[5228]: A serious error occurred in Duplicati: System.PlatformNotSupportedException: Operation is not supported on this platform.
May 5 23:35:29 duplicati duplicati-server[5228]: at Duplicati.Server.Database.ServerSettings.get_ServerSSLCertificate () [0x00115] in :0
May 5 23:35:29 duplicati duplicati-server[5228]: at Duplicati.Server.WebServer.Server…ctor (System.Collections.Generic.IDictionary2[TKey,TValue] options) [0x0029d] in <c71fcbcde8624d2e8a8aa9e50b627014>:0 May 5 23:35:29 duplicati duplicati-server[5228]: at Duplicati.Server.Program.StartWebServer (System.Collections.Generic.Dictionary2[TKey,TValue] commandlineOptions) [0x00000] in :0
May 5 23:35:29 duplicati duplicati-server[5228]: at Duplicati.Server.Program.RealMain (System.String _args) [0x00227] in :0
^XMay 5 23:35:30 duplicati systemd[1]: duplicati.service: Main process exited, code=exited, status=100/n/a
May 5 23:35:30 duplicati systemd[1]: duplicati.service: Unit entered failed state.
May 5 23:35:30 duplicati systemd[1]: duplicati.service: Failed with result ‘exit-code’.
May 5 23:35:30 duplicati systemd[1]: duplicati.service: Service hold-off time over, scheduling restart.
May 5 23:35:30 duplicati systemd[1]: Stopped Duplicati web-server.
May 5 23:35:30 duplicati systemd[1]: Started Duplicati web-server.

what has gone wrong here ? I’ve upgraded mono and a little while before that i’ve upgraded duplicati to the latest release.

Mono 5.20.1.19
Duplicati 2.0.4.17_canary_2019-04-11