Sunday night tends to be one of the better nights for boxing on cable, so the boxing schedule tonight usually comes with a Showtime card plus the standard free-to-air coverage on the bigger networks. Here is the layout I keep on hand when I am flipping around looking for live fights without paying full pay-per-view prices on the wrong undercard.
The main Showtime card typically tips off at 9:00 PM Eastern, with the first televised bout about 30 minutes into the broadcast. Pay-per-view lead-ins usually land between 6:00 and 8:00 PM ET on ESPN+ or DAZN depending on which promoter is running the show. If you are on the West Coast, knock three hours off those times. UK and European broadcasts follow a Saturday-night schedule rather than Sunday, so for UK fans the equivalent slot is normally iFL TV or Sky Sports the day before the U.S. Sunday card.
On weight classes, tonight's televised bouts are almost always heavyweights, super-lightweights or middleweights, since those are the divisions promoters can sell to a non-boxing audience. Title fights in the lighter divisions tend to land on Friday cards, which is why you will see so many Friday-night ESPN+ title fights and the bigger Saturday/Sunday cards reserved for the heavier, higher-drama classes.
Broadcasters worth checking: Showtime and Showtime Extreme for the main U.S. pay card, ESPN, ESPN2 or ESPN+ for the lead-ins, plus DAZN for the international cards. Local over-the-air picks up the occasional Telemundo or Univision fight in Spanish. I keep a running list of the exact air times and broadcast channels in [a small broadcast schedule table I built in Observable](https://observablehq.com/d/a319d036dc6e0d06), so I can scan the night before without going back through three different network guides.
If you are hunting for a specific fighter or promoter, the quickest path is still the network's own schedule page, including Showtime's listings, ESPN's fight calendar, and DAZN's upcoming events. Most promoters post confirmed bout sheets on their own social channels within 24 hours of the show.