this https://github.com/joomla/joomla-cms/blob/staging/installation/sql/sqlazure/joomla.sql#L2883 needs a defaultt value.
Similiar to this one https://github.com/joomla/joomla-cms/pull/13035/files (in this case was mysql).

bottom line is all db systems (mysql, postgresql, sqlazure) need to have a default value in the db table columns when they are set as NOT NULL, normally DEFAULT '' for strings and DEFAULT 0 for integers.

What needs to be done in this cases:

• Add the default value to the joomla.sql installation file for each of the 3 database systems (if they all need)
• Add 1 update files for each of the 3 database systems (if they all need)

This particular case:

• sqlazure (NOT OK): https://github.com/joomla/joomla-cms/blob/staging/installation/sql/sqlazure/joomla.sql#L2883
• mysql (NOT OK): https://github.com/joomla/joomla-cms/blob/staging/installation/sql/mysql/joomla.sql#L1821
• postgresql (OK): https://github.com/joomla/joomla-cms/blob/staging/installation/sql/postgresql/joomla.sql#L1738

So you need to change the mysql and sqlazure joomla.sql file to have DEFAULT '' in the core_xreference and make update sqls for mysql and sqlzaure.

Thanks for your explanation: With this default value it would work:
[core_xreference] nvarchar NOT NULL DEFAULT '',

ok i'm doing a PR to normalize those values in ucm_content table

Please test #13513