Same issue here and we got the same response from our PaaS supplier:
- on iSeries (AS/400) DB2 is on a different port
- use ODBC
But that is indeed slower, plus it requires additional software. That by itself can be overcome, if it weren't for the insane compatibility mess that IBM software is. You need that version of that software that is only compatible with this Windows version, but the data driver is a different version and that is not compatible with the plugin for Visual Studio, etc. etc, ... Combine that with endless vague support documents and you spend hours researching the stuff, without making any progress.
Microsoft could help us a lot by simply allowing a different port in their own DB2 connection driver. Then I could toss all of this iSeries access mess out the door. :-)