[one guy in new jersey]

Is there any state remaining in which the executive has not yet certified a slate of electors, or has that been done in all 50 states?

[Lurking Libertarian]

Is there any state remaining in which the executive has not yet certified a slate of electors, or has that been done in all 50 states?

All 50 states & D.C. have certified. Forty-nine of the 50 states (and D.C.) certified by the Safe Harbor deadline, which is supposed to preclude even challenges in Congress.

[Reagan80]

California did so on December 5; which gave Biden 270+ electors from certified slates.