What I expected to happen was...:
/scoreboard players list * lists all the scores for all entities tracked by the scoreboard. This was the case in older versions, and is used in the telegraf Minecraft plugin to collect statistics. It is also documented in the Minecraft wiki scoreboard page.

What actually happened was...:
/scoreboard players list * says:

[19:31:06] [Server thread/INFO]: No relevant score holders could be found

There are definitely players in the scoreboard:

/scoreboard players list
[19:31:41] [Server thread/INFO]: There are 25 tracked entities: ...

Steps to Reproduce:
1. Create a scoreboard objective, and add a player to be tracked by it.

2. Run /scoreboard players list * and notice that no players could be found.