Totally anecdotal, but at the biggest theatre in my area, on the biggest screen, the 6pm showing of The Flash this evening (Wednesday openings here in Australia), 7 tickets had sold when I checked at around 3pm. Dial of Destiny at the same 6pm showing same screen two weeks later, has sold 5 tickets. The 9pm showing tonight has sold 1 ticket. Thursday 6pm, 1 ticket. Friday 6pm, 1 group of 4 tickets. Hell, Spider-Verse in non-premium format has sold 12 tickets for its 7:45pm showing tonight. The Flash's non-premium 7pm showing (nearest comparison) has sold 9 tickets.
I can almost count on one hand the number of premium screen 6pm tickets The Flash has sold for its opening Wednesday, Thursday and Friday.
Whilst it's just one cinema in one city of Australia, it's painting a really dire situation for The Flash.