I’ve just put it into a build which uses Applovin Max for mediation. I haven’t rolled out the build to the public yet so can’t say whether it has any effect yet, but it doesn’t seem to cause any problems when adding it so I would suggest there is no harm in trying it out.
The mediation SDKs just use wrapped versions of the ad networks SDKS, so adding these lines to build.settings will in turn add them to AndroidManifest.xml which is where the ad network SDK will be looking for them. Both ironSource and Applovin Max are using versions of the Admob SDK which is higher than 21.0.0, so this should work on both.