I would like to be able to synchronise a DB2/AS400 database with a Google sheet in order to use it with a Google Appsheet.
Is there a way to do this with Appscript for example?
Use Java and JDBC as decribed by this question and answer -- How to connect Google Sheets to Database.
Just use the JTOpen JDBC driver (https://sourceforge.net/projects/jt400/) to connect to Db2 for i.