I am trying to convert a large Lucidchart diagram that took quite a while to Draw.io. Draw.io recommends ctr-a, ctr-c, ctr-v, but that doesn't seem to be working. Draw.io also cryptically mentions however:
draw.io supports importing the Lucidchart JSON file format. Lucidchart makes it difficult to obtain that data, so the easiest way to import is to copy and paste from editor to editor.
Has anyone ever figured out how to get the this json from Lucidchart?
Essentially, you're asking about Lucidchart's JSON exportability. Lucidchart supports JSON export from their Cloud Insights product - and steps on how to export here.
Note: this is not going to work for the standard ULM or chart style diagrams, and JSON isn't one of the current export options for the standard diagrams.
One thing you could try to hack together would be to connect your Lucidchart account to one of Zapier's two "search" actions, and then use a trigger to send and structure that data to an application like Firebase / Cloud Firestore. Once in the database, you could export the JSON file. (I haven't tried this particular use case before, but have used Zapier to successfully create a JSON tree structure from data coming from multiple applications). Hope this is helpful.