Disabled custom app per 1 jan 2026

We want to add a Fulfillment integration for a shop today, we already have multiple shops integrated. Now we need another. But the method does not work anymore because the direct Admin API access key is not available anymore.
Now we need to implement an OAuth flow to get that token. Which obviously is not done in one day. Even with AI we cannot implement this new flow that fast.
Can this customer get this legacy personalized app enabled or another work around to get this working fast?

I’d say no.

This is the closest option Using the client credentials grant
Still needs to be reacquired daily.