Parse error and missing valid Swagger or OpenAPI version field

I am using the following packages:

• Swashbuckle.AspNetCore 5.0.0-rc2
• Microsoft.AspNetCore 2.2,
• Microsoft.AspNetCore.Authentication.AzureAD.UI 2.2.0
• Microsoft.AspNetCore.Mvc 2.2.0
• Microsoft.AspNetCore.Mvc.Versioning 3.1.2
• Microsoft.AspNetCore.Mvc.Versioning.ApiExplorer 3.2.0

I have set everything up to use OpenAPI. When adding swagger generation with the code below I get:

• “Parser error on line 201 missed comma between flow collection entries” and “missing valid Swagger or OpenApi version field”.
• “Unable to render this definition The provided definition does not specify a valid version field. Please indicate a valid Swagger or OpenAPI version field. Supported version fields are swagger: “2.0” and those that match openapi: 3.0.n (for example, openapi: 3.0.0).”

services.AddSwaggerGen(options =>
            {
                options.AddSecurityDefinition("bearer", new OpenApiSecurityScheme
                {
                    Type = SecuritySchemeType.Http,
                    Scheme = "bearer",
                    BearerFormat = "JWT",
                    Description = "JWT Authorization header using the Bearer scheme. Example: \"Bearer {token}\"",
                    Name = "Authorization",
                    In = ParameterLocation.Header,
                    Flows = new OpenApiOAuthFlows
                    {
                        Implicit = new OpenApiOAuthFlow
                        {
                            AuthorizationUrl = new Uri($"https://login.microsoftonline.com/{configuration["AzureAD:TenantId"]}/oauth2/authorize", UriKind.RelativeOrAbsolute),
                            Scopes = new Dictionary<string, string>
                            {
                                {
                                    "user_impersonation", "Access api"
                                }
                            }
                        }
                    }
                });

                options.AddSecurityRequirement(new OpenApiSecurityRequirement
                {
                    {
                        new OpenApiSecurityScheme
                        {
                            Reference = new OpenApiReference { Type = ReferenceType.Header, Id = "Authorization" }
                        },
                        new[] { "user_impersonation" }
                    }
                });

I may be doing things wrong, but I have tried to find ways to do this and it seems to me that there are settings/properties missing. Please enlighten me, is this is a bug or not. Kind regards Thomas