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 188.8.131.52 DB
Thank you mxallen-oracle. I entered a Oracle SR and it was also confirmed that the 184.108.40.206 Gateway product is certified with Oracle 220.127.116.11 on AIX 7.1
Yes, Oracle Database Gateway for SQL Server 18.104.22.168 is certified on AIX 7.1.
But I recommend to install Oracle Database Gateway for SQL Server 22.214.171.124 which is certified on AIX 7.1 and also certified with Oracle database 126.96.36.199.
You can download the gateway from MOS - Patches & Updates:
21419221 - 188.8.131.52.0 PATCH SET FOR ORACLE DATABASE SERVER