Trying to find Lapis Lazuli Ore is very difficult as spawning tries appear to be less as well as spawn size in comparison to 1.12.

Whilst this is not exactly a bug but an internal setting, I feel nonetheless it is a bit of a game breaker and needs attention early before final release. This is why I added it as a bug. As worlds will already be generated after release, this setting will be difficult to change and have affect on already created chunks.

Lapis ore being rare will be worse on servers where shipwrecks and treasure will have been raided by other players.

 As Lapis is used for enchanting and dying items its scarcity is proving to be difficult.

From clearing many of the lower two sub-chunks of other blocks with the fill command, I can see that it is spawning but in very low quantities and is very much harder to find than diamonds.

Having looked at a number of default generated worlds I would recommend changing the spawn tries and spawn size slightly to change the balance.