Order a query result by a numeric meta key even if it does not exist, but put the posts with meta key first

I want to order a WP Query result by a numeric meta value in PHP.

To achieve this, I am doing as follows:

Where the meta key is called orden_en_categ.

And what is the problem?

This query setting is displaying posts in the following order:

I want the posts without meta appear after the posts with meta, as follows:

Where the order of the posts without meta does not matter.

The default meta solution:

I know I could add a default meta to all posts with a value of something like 999 and this would work. But, there must be an alternative way, without having to add those sticky meta values.