The California Secretary of State’s web page now lists the candidates in the March 3, 2020 primary.
Here is a link to the presidential primary candidate list. The list is alphabetical and combines candidates from all six parties into a single list.
Here is a link to U.S. House candidates.
Here is a link to State Senate candidates.
Here are the Assembly candidates.
Thanks to Mark Seidenberg for the links. Every U.S. House race has at least two major party members running, so under the top-two system, the November ballot will not include any candidates except Republicans and Democrats.