I practice OMAD and in general just add generous amounts of salt to just about everything solid that enters my mouth and isn’t fruit; on hot or especially active days I might add some to my water or coffee as well (though the latter I tend to get salty over not being bitter). Rationale being mild propensity for hypotension plus dietary choices that for the most part come without added salt.
Magnesium-wise, I’m not prone to cramps and if anything I saw a decline in occurrence frequency since adopting IF (no idea whether it’s been a consequence of IF per se, weight loss, or saner food choices). Sporadically I take a tablet.
In terms of potassium and calcium, I’ve never had any particular complaint that could hint at their shortage either (though I admittedly suck at listening to my body). I’d like to believe that they are taken care of by my reasonably balanced diet. Phosphorus might be worth taking a closer look at, as nothing on my table is a particularly solid provider.
As always the proper advice (which I should myself learn to follow every now and again) is: Consult your GP, get your levels checked, act accordingly.