I have no doubt that schedulix will run flawlessly in combination with PG11.
Since schedulix can operate with a range of database systems, it uses only core functionality of standard SQL.
INSERT INTO <tablename> (<column-list>) VALUES (<value-list>);
UPDATE <tablename> SET <assignment-list> WHERE ID = <long>;
UPDATE <tablename> SET <assignment-list> WHERE ID = <long> AND VALID_TO = <MAX_LONG>;
DELETE FROM <tablename> WHERE ID = <long>;
(Note that the primary key of a table is either ID, or the combination of ID and VALID_TO).
No database system will get exited about such kind of queries.
At startup time some complex joins are executed. But the query text is, apart from a few details like quoting, the same for all supported DBMS.
It is therefore very unlikely that they won't execute on PG11.
Now since we want to be compatible with PG11 as well, please report any issues immediately.
I'll treat them with priority and it is very likely you'll receive a fix at the very same day.