What is the use of ip-geolocation for LTM?

Decide based on country/region/etc... what to do

1- redirect to a closer datacenter (similar to gtm )

2- redirect to a specific version/localization of your websites (language, currency)

3- block some features from specific country (banking financial and insurance have some restrictions when selling service outside of their country)

so it act as gmt

GTM and DNS are different kind of load-balacing!

but you can find some small similarity: dns redirect users using dns response, ltm redirect users using http response.