I’d like to throw a caution out there on this one. Just for the record, I’m leaving mine alone (2014 Legacy).
With these CVT transmissions, there is a lot that go wrong with a simple fluid change. If you are going to do it, the dealer would probably be the safest place to have it done. If you have an independent shop do it, make sure they are using the correct fluid and following the correct procedures. The will need a scan tool that can monitor the ATF temperature because the fluid level has to be set a specific temperature which appears to NOT be ambient or the normal operating temperature of the ATF.