The reported behavior repros in 4.20 and 4.21, but does not repro in 4.19.
Regarding the "Literal Enum" node in blueprints:
When an input enum value is connected to the input pin, the output is always the first enum value (index 0) regardless of input value. (This behavior is in error)
If the Literal Enum node's input pin is disconnected, then the output will properly match the value selected in the dropdown. (This is expected behavior).
Given an enumeration with "First_0", "Second_1" and "Third_2" values, the attached BP graph produces the following Output:
Byte value used: 2
Byte as Enum: Third_2
Literal with Input Pin: First_0
Preset Literal: Third_2
Output number 3 is in error.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-64570 in the post.