Wp-admin wrongly redirecting on multisite

Solved it adding an annotation to the ingress:

nginx.ingress.kubernetes.io/rewrite-target: /
nginx.ingress.kubernetes.io/use-regex: "true"
nginx.ingress.kubernetes.io/configuration-snippet: |
  rewrite ^(/[^/]+)?(/wp-admin)$ $1$2/ break;
  rewrite ^(/[^/]+)?(/wp-admin/.*)$ $1$2 break;

And changing the pathtype to ImplementationSpecific