Code that works just fine in v9.0.4 causes the application to hang indefinitely in v10.0.1.
Reproduction:
string connString = "Host=localhost;Port=5432;Username=user;Password=pwd;Database=database";
NpgsqlConnectionStringBuilder connectionStringBuilder = new(connString);
NpgsqlDataSource? dataSource = NpgsqlDataSource.Create(connectionStringBuilder);
await using (NpgsqlConnection pConnection = await dataSource!.OpenConnectionAsync()) ← permanent hang
When I pause in the debugger, I can see one thread with a pretty huge call stack that appears to be somewhere down in the security end of things. Downgrading to 9.0.4 fixes the problem.

Code that works just fine in v9.0.4 causes the application to hang indefinitely in v10.0.1.
Reproduction:
When I pause in the debugger, I can see one thread with a pretty huge call stack that appears to be somewhere down in the security end of things. Downgrading to 9.0.4 fixes the problem.