In 1.12, the output of "/scoreboard objectives list" looked like this:

Showing 2 objective(s) on scoreboard:
- Objective1: displays as 'First Objective' and is type 'xp'
- Objective2: displays as 'Second Objective' and is type 'dummy'

Now it looks like this:

There are 2 objective(s): [First Objective], [Second Objective]

There is also no other way to see the type of a scoreboard without an external tool, except for "trigger", which is seen in the autocomplete of "/scoreboard players enable @s ".