Due to the FOX Network having the broadcast rights to the MLB's World Series, a future SmackDown episode is going to be moved out of its usual Friday night slot on the network.
FOX Sports released their broadcast schedule for October, and the October 23 episode of SmackDown will be pre-empted in favor of Game 3 of the World Series.
WWE has not announced when that week's SmackDown will air, or on what channel.
When and wherever SmackDown airs that week, it will serve as the go-home broadcast for the Hell in a Cell pay-per-view on October 25.
Based on what happened last year, it's most likely that SmackDown would simply move to cable channel Fox Sports 1 for a week. Game 3 of the 2019 World Series aired on a Friday night, and resulted in that evening's SmackDown being moved to FS1. Notably, that one-week move resulted in SmackDown doing under one million viewers.
There is also the matter of the October 16 episode of SmackDown. If the National League Championship Series goes to a fifth game (in a best of seven), SmackDown could possibly be pre-empted on that night as well.