Piranha.IdentityServer4.Auth

 services.AddPiranha(options =>
            {
                options.AddRazorRuntimeCompilation = true;

                options.UseFileStorage(naming: Piranha.Local.FileStorageNaming.UniqueFolderNames);
                options.UseImageSharp();
                options.UseManager();
                options.UseTinyMCE();
                options.UseMemoryCache();
                options.UseEF<SQLiteDb>(db =>
                    db.UseSqlite(_config.GetConnectionString("piranha")));
                options.UseIdentityServer4Auth(ids4Options =>
                {
                        ids4Options.SignInScheme = "Cookies";
                        ids4Options.Authority = "https://identityserver4.io";
                        ids4Options.ClientId = "client id";
                        ids4Options.RequireHttpsMetadata = false;
                        ids4Options.ResponseType = "code id_token";
                        ids4Options.SaveTokens = true;
                        ids4Options.GetClaimsFromUserInfoEndpoint = true;
                        ids4Options.UseTokenLifetime = false;
                        ids4Options.ClientSecret = "your secret key";
                        ids4Options.Scope.Add("your scope");
                        ids4Options.AuthenticationMethod = OpenIdConnectRedirectBehavior.FormPost;
                });
            });

Configuration

it's a standart oidc client parameters

options.UseIdentityServer4Auth(ids4Options =>
                    {
                        ids4Options.SignInScheme = "Cookies";
                        ids4Options.Authority = "https://identityserver4.io";
                        ids4Options.ClientId = "client id";
                        ids4Options.RequireHttpsMetadata = false;
                        ids4Options.ResponseType = "code id_token";
                        ids4Options.SaveTokens = true;
                        ids4Options.GetClaimsFromUserInfoEndpoint = true;
                        ids4Options.UseTokenLifetime = false;
                        ids4Options.ClientSecret = "your secret key";
                        ids4Options.Scope.Add("your scope");
                        ids4Options.AuthenticationMethod = OpenIdConnectRedirectBehavior.FormPost;
                    });