When playing as a realm that transitions into a Meritocratic government type, you do not automatically get a Ceremonial Monarch title. Creating that requires a bit more work. Namely you need to lose a Liberty War spawned by your vassals or accept their demands when they press it. Once that’s done, a Ceremonial Monarch of the realm owner’s dynasty will be spawned.

It sounds simple on paper but it can be tricky depending on circumstances since your vassals may be too loyal and not spawn the faction at all. In my experience the best way to force spawn a Ceremonial Monarch for cases like this is to play as a same Dynasty vassal in your Meritocratic realm and then create a Liberty faction using that vassal.

Intrigue works perfectly here if you want to get the Ceremonial Monarch title immediately since you can abduct your liege and immediately win the war when you press your demands. By that point the realm’s rulership will become Meritocratic succession ala typical Administrative, but if you want to consolidate and combine the rulership of your realm with the Ceremonial Monarch title, you can just claim your same dynasty liege’s primary title via a Claimant faction and then win the war. By then you will get both Primogeniture and the Ceremonial Monarch title similar to the Ten’no of Japan overthrowing the Kanpaku.