IdentityServer settings configuration to use it with SPA that is not hosted with IdentityServer. For example, we have client app on http://localhost:4200 and backend app on https://localhost:5001. To allow working it, we need to set/change “Profile” to “SPA”. Additional we can configure “RedirectUri” and “LogoutUri”.
Backend side (.NET Core 3.1).
Code snippet of appsettings.json:

// "IdentityServer": {
// "Clients": {
// "crypto-web-app": {
// "Profile": "IdentityServerSPA"
// }
// }
// },
"IdentityServer": {
"Clients": {
"crypto-web-app": {
"Profile": "SPA",
"RedirectUri": "http://localhost:4200/authentication/login-callback",
"LogoutUri": "http://localhost:4200/authentication/logout-callback"
}
}
},