Hi,
I did some researches on Internet and I found a solution to solve my problem.
The table com_content_types was empty. I filled it with the 13 missing records. And good news, now it works.
I have been able to migrate all my K2 categories, K2 tags and K2 articles to Joomla articles.
Now, I am going to migrate my extension (Raxo and some others) to take into accounts the new articles.
Then I will migrate to Joomla 4.
Thanks for your help.
Sincerely,
A. Guillen