Thanks for the kind words!
For the backend I used Firebase and just POST/GET json data using an HTTPRequest node. For the panel on Godot side, it is just a VBoxContainer to which I add children nodes of type "LeaderboardEntry", which is just a scene made up of an HBoxContainer filled with two labels.
# Clear board
for child in $ScoresBox.get_children():
child.queue_free()
# Fill table
var scores = GameController.load_scores()
for score in scores:
var entry = leaderboard_entry.instance()
entry.name = score[0]
entry.time = "%s" % GameController.format_time(score[1])
$ScoresBox.add_child(entry)