Could it be that your supabase project was paused and restored recently? This announcement says that: “Projects restored from 1st May 2025 will no longer be restored with the legacy API keys.” This might not be a change in how n8n works, but a new restriction on how API keys work in Supabase. At least that’s the first thing I would try to check. Edit: This wouldn’t apply to a self-hosted, non-https Supabase host.
If you find that you need to set up a local https redirect URL, you could look into Self Hosting n8n with Docker and Traefik/LetsEncrypt (for https)