You are missing out few, will try to answer in chronology:
From Supergirl S05E08:
Tim Burton's Batman Movies: Alexander Knox (Robert Wuhl) cameo who was the first to report upon The Joker's crimes
Titans: Hawk (Alan Ritchson) and Jason Todd (Curran Walters) cameo
Batman (1966 TV series): Robin (Burt Ward) shouts "Holy Crimson Skies Of Death!"
Freedom Fighters: The Ray We see Russell Tovey flying in his Ray costume.
Then, of course, we see Supergirl, The Flash, Arrow, Batwoman and Legends of Tomorrow characters
From Batwoman S01E09
Smallville: powerless retired Clark Kent and Lois Lane.
Superman Returns: Brandon Routh Superman (costume from Kingdom Come TPB)
Batman: Kevin Conroy as Batman in the future
Jonah Hex: Johnathan Schaech as Jonah tries to prevent Oliver's resurrection in the Lazarus Pit
From The Flash S06E08
Birds of Prey (2002 TV series): Helena Kyle Cameo
Lucifer: Lucifer cameo
The Flash (1990 TV series): Flash (John Wesley Shipp) appears
Black Lightning: Black Lightning cameo