Rare enemies drop better loot and are worth a detour while leveling. Two add-ons help find them.
SilverDragon
SilverDragon watches nameplates, your target and the minimap for rares and announces them. Its author added minimap-tracking scanning for Forever in a recent release.
RareScanner
RareScanner shows a panel with a target button when it detects a rare, treasure or event, and marks known spawns on the map. Its author notes that Forever, like Classic, has no map vignettes, so it detects less than on retail.
What that means
On retail, the game marks many rares on the minimap and these add-ons read those marks. Forever has fewer of them, so detection relies more on nameplates and your own exploring. Spawn data for the new zones also has to be collected first.
Pick one
Running both doubles every alert. Start with SilverDragon for quiet announcements, or RareScanner if you like its panel and map pins. Both have Forever builds.