i spent one week to anderstand why i have an issu to connect with portenaire.
in your doc you have inverse two lines in step 2.

You should put the Redirect URL underneath Resource URL as it is in portenaire to solve the problem. Because it in this order in portenaire

OAuth Configuration

Client secret
Authorization URL
Access token URL
Resource URL
Redirect URL
Logout URL
User identifier
Scopes
Actions

and not
OAuth Configuration

Client secret
Authorization URL
Access token URL
Redirect URL
Resource URL
Redirect URL
Logout URL
User identifier
Scopes
Actions

Step 2 - Portainer
In Portainer, under Settings, Authentication, Select OAuth and Custom

Client ID: Client ID from step 1
Client Secret: Client Secret from step 1
Authorization URL: https://authentik.company/application/o/authorize/
Access Token URL: https://authentik.company/application/o/token/
Redirect URL: https://portainer.company
Resource URL: https://authentik.company/application/o/userinfo/
Logout URL: https://authentik.company/application/o/portainer/end-session/
User Identifier: preferred_username (Or email if you want to use email addresses as identifiers)
Scopes: email openid profile

thgank u for your job