ERROR: new collation (en_US.UTF-8) is incompatible with the collation of the template database (en_US.utf-8)

Hi all,

while doing `cat pg_dump.dump | psql` I get the above message. Note that 
`pg_dump.dump` contains:

     CREATE DATABASE some_db WITH TEMPLATE = my_own_template ENCODING = 
'UTF8' LC_COLLATE = 'en_US.UTF-8' LC_CTYPE = 'en_US.UTF-8';

What is exactly the problem? I understand that en_US.UTF-8 and 
en_US.utf-8 is not *exactly* the same string.

However I do not understand how the difference came to be. And I do not 
know what the "right" way is and how to proceed from here.

If I `pg_dump --create` some DB on the new server (13.7-1.pgdg18.04+1) I 
get:

     CREATE DATABASE ... ENCODING = 'UTF8' LOCALE = 'en_US.utf-8';

When I do the same on the old server (12.8-1.pgdg20.04+1) I get:

     CREATE DATABASE ... ENCODING = 'UTF8' LC_COLLATE = 'en_US.UTF-8' 
LC_CTYPE = 'en_US.UTF-8';

Any hints or help?
*t