1) “Abbott Elementary” (shown here) season-opener, 9:30 p.m, ABC. Stranded between a reality show (“Golden Bachelorette”) and a news report, this is a lonely comedy island. It deserves more; in each of its first three seasons, it was the only broadcast show nominated for the best-comedy-series Emmy. Now the school year starts amid some nearby construction chaos.
2) “The Secret Life of Diddy,” 10:02 p.m., ABC. This was supposed to be the debut of “Scamanda,” a documentary series about a young woman convicted of a scam, faking cancer to scam. Now that’s been delayed a week for this report on Sean “Diddy” Combs, the music mogul accused of sexual assault.
3) “Secrets of the Dead,” 10 p.m., PBS. Maria “Nanneri” Mozart was a gifted pianist and, apparently, a composer. But when she began learning to play, her 3-year-old brother Wolfgang was nearby. He became a phenom; she was his fan, but faded from public view as an adult. Here’s a fascinating look at the efforts to find artifacts of a strong talent.
4) “Joan,” 9 p.m., CW. Joan – played with subtle skill by Sophie Turner of “Game of Thrones” – is at a turning point in this true story. She keeps getting better as a jewel thief and scam artist, but further away from retrieving the daughter who’s in family services. Tonight brings highs and lows.
5) “The Masked Singer,” 8 p.m., Fox. So far, the show has dumped former quarterback John Elway and actress Yvette Nicole Brown. It’s in a crowd at 8 p.m., facing CBS’ “Survivor,” CW’s “Sullivan’s Landing” (Sully is stunned by his diagnosis), “NBC’s “Chicago Med” and more.