Updated answer as of 2022:
Major Appearances:
A Full Course Tag Battle! DP076 (Glaceon's anime debut)
Strategy With a Smile! DP079
All for the Love of Meloetta! BW085
Team Eevee and the Pokemon Rescue Squad! BW102
Curtain Up, Unova League! BW103 (appears in flashback)
Lost at the League! BW105
Eevee & Friends PK25
Turning Heads and Training Hard! SM065
Smashing With Sketch! SM066 (appears in Poke Problem segment of the episode)
Breaking the Ice! JN087
JN115 (Appears in flashback)
Minor Appearances:
A Lean Mean Team Rocket Machine! DP092
Giratina and the Sky Warrior M11
PK19
Sliding Into Seventh! DP127
A Marathon Rivalry! DP160
An Old Family Blend! DP182
Tag Team Battle Inspiration! XY090 (appears in Shauna's fantasy)
A Dancing Debut! XY101
Master Class Choices! XY109
Master Class Is in Session! XY112
A League of His Own! XY125
Loading the Dex! SM003 (appears in Meowth's fantasy, but was an illusionary disguise of Gastly, Haunter, and Gengar)
A Talent for Imitation! JN019 (appears on a Pokedex image)
To Train, or Not to Train! JN049
On Land, In the Sea, and to the Future! JN063 (appears in fantasy)
Source
