.Net5 SslStream throws OpenSslCryptographicException: error:14094416:SSL routines:ssl3_read_bytes:sslv3 alert certificate unknown

# SslStream throws OpenSslCryptographicException: error:14094416:SSL routines:ssl3_read_bytes:sslv3 alert certificate unknown

I wrote a simple http server with SslStream which works fine under .net core 3.1, but throws this OpenSslCryptographicException since i've upgraded to .net5.

` public SslProtocols AllowedSslProtocols { get; set; } = SslProtocols.Tls13 | SslProtocols.Tls12 | SslProtocols.Tls11;`

---> Interop+OpenSsl+SslException: SSL Handshake failed with OpenSSL error - SSL_ERROR_SSL.
---> Interop+Crypto+OpenSslCryptographicException: error:14094416:SSL routines:ssl3_read_bytes:sslv3 alert certificate unknown
--- End of inner exception stack trace ---
at Interop.OpenSsl.DoSslHandshake(SafeSslHandle context, ReadOnlySpan`1 input, Byte[]& sendBuf, Int32& sendCount)
at System.Net.Security.SslStreamPal.HandshakeInternal(SafeFreeCredentials credential, SafeDeleteSslContext& context, ReadOnlySpan`1 inputBuffer, Byte[]& outputBuffer, SslAuthenticationOptions sslAuthenticationOptions)
--- End of inner exception stack trace ---
at System.Net.Security.SslStream.ForceAuthenticationAsync[TIOAdapter](TIOAdapter adapter, Boolean receiveFirst, Byte[] reAuthenticationData, Boolean isApm)
at System.Net.Security.SslStream.ProcessAuthentication(Boolean isAsync, Boolean isApm, CancellationToken cancellationToken)
at System.Net.Security.SslStream.AuthenticateAsServer(SslServerAuthenticationOptions sslServerAuthenticationOptions)
at System.Net.Security.SslStream.AuthenticateAsServer(X509Certificate serverCertificate, Boolean clientCertificateRequired, SslProtocols enabledSslProtocols, Boolean checkCertificateRevocation)
at NHttp.HttpClient..ctor(HttpServer server, TcpClient client)
20-11-17_17:49:51[Debug]HttpClient:System.Security.Authentication.AuthenticationException: Authentication failed, see inner exception.
---> Interop+OpenSsl+SslException: SSL Handshake failed with OpenSSL error - SSL_ERROR_SSL.
---> Interop+Crypto+OpenSslCryptographicException: error:14094416:SSL routines:ssl3_read_bytes:sslv3 alert certificate unknown
--- End of inner exception stack trace ---
at Interop.OpenSsl.DoSslHandshake(SafeSslHandle context, ReadOnlySpan`1 input, Byte[]& sendBuf, Int32& sendCount)
at System.Net.Security.SslStreamPal.HandshakeInternal(SafeFreeCredentials credential, SafeDeleteSslContext& context, ReadOnlySpan`1 inputBuffer, Byte[]& outputBuffer, SslAuthenticationOptions sslAuthenticationOptions)
--- End of inner exception stack trace ---
at System.Net.Security.SslStream.ForceAuthenticationAsync[TIOAdapter](TIOAdapter adapter, Boolean receiveFirst, Byte[] reAuthenticationData, Boolean isApm)
at System.Net.Security.SslStream.ProcessAuthentication(Boolean isAsync, Boolean isApm, CancellationToken cancellationToken)
at System.Net.Security.SslStream.AuthenticateAsServer(SslServerAuthenticationOptions sslServerAuthenticationOptions)
at System.Net.Security.SslStream.AuthenticateAsServer(X509Certificate serverCertificate, Boolean clientCertificateRequired, SslProtocols enabledSslProtocols, Boolean checkCertificateRevocation)

I've found this link concerning SslStream breaking changes:
https://docs.microsoft.com/en-us/dotnet/core/compatibility/cryptography
but didn't get a clue.