Chen, Lu and Read, James (2023) Is the metric signature really electromagnetic in origin?The paper is interesting, but the 4-metric signature +++- is mainly a consequence of causality, be it electromagnetic or anything else.
Causality requires that events only affect nearby events. If spacetime were Euclidean, with metric signature ++++, then an event could be close to an event outside its light cone. Affecting that nearby event would mean going faster than light. Action at a distance.
Electromagnetic effects do not go faster than light. You need the non-euclidean geometry of a +++- signature metric. Once you accept all that, Maxwell's electromagnetism is one of the simplest possible field theories, compatible with the geometry.