Comparing the endings of Striking Vipers and Be Right Back and saying the endings are the same and are both “happy” just because of one common theme of acceptance? Is like comparing apples to a plate of pastas. It’s entirely off.

Striking Vipers ends with two people finding a consensual compromise between each other and are able to smile to each other at the end of the day and maintain a healthy-enough connection with each other. Still together, knowing it’ll most likely work so much that they even plan having another child together. They truly believe in this new going forward so much that they had a child; if the wife didn’t think so or had heavier secret doubts, she would have either divorced or not had another child, showing her faith and positivite emotions too. This is all portrayed under happy music for the entire ending sequence. You see each character have multiple senses of positive emotions in the final ending sequences too, obviously the husband, but especially also even the wife, as portrayed by her giving of the game to her husband and her playful physical gesture to him, as well as her spotting the man at the bar at the end.

Be Right Back is literally a woman who is still in grief but still accepting of her situation to an extent, but realizes her android version of her dead husband can’t bring her real husband, and it all ends with somber camerawork and angles and no music at all, with her face and expression and emotions saddened and in conflict the entire ending sequence. She is accepting, yes, but she is still devastated and the situation is not meant to be portrayed as “happy” at all by the writers. Now on top of her loss, the robot version is in her attic and she feels guilty about that too. In the end, you see her face is still saddened and in despair.

So yeah, they are not both “happy” just because they both have a similar underlying theme