Searching TV Guide doesn't show anything except TNG reruns on BBC. That can't be comprehensive, though -- TOS is in syndication on local channels all the time. At least, it was the last time I actually spent time at someone's house where they had cable (maybe six weeks ago).
Honestly, I mostly stick to Netflix these days. It's really the only affordable option (for me).
TOS is in syndication with MeTV, they have a Saturday night block of Sci-Fi and Fantasy shows.
So aside from that and TNG on BBC America there is no other regular national syndication of Trek in the USA right now. Which is a huge shame, in the late-90s to early-2000s Trek was easily available on TV.
As you pointed out, the wide availability of Trek on streaming services (Amazon Prime, Netflix, and Hulu all have Trek) may be part of the reason why we don't see it on linear TV much right now.