If the app shows Google Maps: a restricted key

Open Google Maps Platform → Keys & Credentials, Create credentials → API key. Then Edit API key: under Set an application restriction choose Android apps → + Add → package {{fodidePackage}}, SHA-1 {{fodideSha1}} (make a second key for iOS with iOS apps → bundle {{fodideBundleId}}). Under API restrictions choose Restrict key and tick only Maps SDK for Android (or for iOS). Save. Paste the key in Fodide where it asks.

Maps needs a billing account on the project (step 9). The map key is the one key that lives in the app, which is why it is locked to the app's package and signature.