The client application creates two Quic connections the first connection install a certificate verification callback that blocks the calling thread, the second connection install a certificate verification callback that accepts all certificates, the ConnectAsync call for the second connection doesn't complete until the certificate verification callback of the first connection returns.
Start the server
dotnet run --project server/server.csproj
Start the client
dotnet run --project client/client.csproj
Blocking remote certificate validation callback
Releasing remote certificate validation callback
Non blocking remote certificate validation callback
Elapsed: 00:00:28.1249768
Tested with .NET 7.0.100-rc.2.22477.23 & Ubuntu 22.04.1 LTS