> Question for Supabase: Is it possible to just have a form with username + password and POSTing the login details?
Yes this is how basic email+password sign-in works. No redirects are necessary. For the rest of the flows, some form of redirect is mandatory because that's how the authentication protocols work and we've found it convenient to implement other logins like magic links, email confirmations, etc.
> Question for Supabase: Is it possible to just have a form with username + password and POSTing the login details?
Yes this is how basic email+password sign-in works. No redirects are necessary. For the rest of the flows, some form of redirect is mandatory because that's how the authentication protocols work and we've found it convenient to implement other logins like magic links, email confirmations, etc.