You can always install the Gateway on a separate server than the DB, thus using a certified environment. You can install the 11g gateway on an Oracle Linux server...
You can use the 12.1 Gateway with an 220.127.116.11 DB
Thank you mxallen-oracle. I entered a Oracle SR and it was also confirmed that the 18.104.22.168 Gateway product is certified with Oracle 22.214.171.124 on AIX 7.1
Yes, Oracle Database Gateway for SQL Server 126.96.36.199 is certified on AIX 7.1.
But I recommend to install Oracle Database Gateway for SQL Server 188.8.131.52 which is certified on AIX 7.1 and also certified with Oracle database 184.108.40.206.
You can download the gateway from MOS - Patches & Updates:
21419221 - 220.127.116.11.0 PATCH SET FOR ORACLE DATABASE SERVER