Hello,
original post now deleted after addition of Edit #2.  Was totally incorrect.
Edit:
Based upon your comment have deleted above.
Have tested the sample in the link provided and have had problems.  While I can add new records (as shown), and I can modify the name field, changing an existing department using this method (query) produces the error shown - this on Ubuntu 18.04 using LO v6.3.0.4.
As asked in comment please elaborate on what you are looking to accomplish and there may be a different method.
Edit #2:
OK, have found the problem with the linked post answer.  It is in the Query.  Using the Right Outer Join is the cause.  But to correct the situation had to use a different method only through SQL View.  Therefore you cannot use the graphical interface.  Have attached a sample based upon you original post.  This sample does NOT include the macro referred to in the linked post.  You can add that if you wish a refreshed list after each modification.  Up to You.
sample ---- FKproblem.odb