Gfortran 10 added the default behavior to make type mismatches an error instead of a warning.
Legacy Fortran programs too often did not explicitly specify the procedure interfaces to allow implicit polymorphism.
The Fortran 2008 standard cleaned up this situation in part with
Gfortran 10 also added flag
-fallow-argument-mismatch, which can be used to degrade the errors to warnings.
It is however
to fix the problem in the legacy code, if it’s part of your code ownership.