I can successfuly export to JSONL. However, I am not able to change the JSON format to other available formats such as JSON_LINES, ARRAY_JSON, JSON or JSON_ID_AS_KEYS. According to the documentation the following should work but it does not:
Weird it worked for me, might the way you return your result too.
For me, even with the JSON_ARRAY format it wasn't what i needed for keylines so I just did it manually with a bunch of map and collect.
What's your version of APOC? You can open the plugin folder using the tree dots by the blue open button and chose Open Folder -> Plugins. Copy and paste the path showed into your file manager if it doesn't open.
In the plugin folder, you can see your APOC version on the apoc file name.