Executive Summary: Both SNS and LRT have become proper Japanese logograms.
SNS has for years been used as the Japanese logogram for the Japanese word エスエヌエス (ESUENUESU), which is Japanese for social media.
I suspect that few Japanese users of the initialism SNS realize what it stands for, and it should be no surprise that few native English speakers use the initialism, although strictly speaking it does have an origin that can be initialized as SNS. But to everyday walking-around people, it’s social media.
The pronunciation of SNS as the Japanese word ESUENUESU is now accepted, is used by countless media, and can even be seen on government websites, without explanation. For example, on https://www.soumu.go.jp/main_sosiki/joho_tsusin/security/kids/sns/index.html, a page aimed at providing guidance to children in using social media, we find “SNS（エスエヌエス）を使うときの注意”
Enter LRT, which to many in-the-know native English speakers is the initialism for light rail transit. The recent introduction into Japan of this tram-like system has caused LRT to pop up frequently in the news, and accidents involving run-ins with cars have boosted its frequency of occurrence in the media.
As far as I can tell, and certainly on various Japanese-language NHK and Nikkei media, the initialism LRT is voiced as エルアールティ(ERUAARUTEI), and is most often followed with a gloss (both in print and orally) of 次世代型路面電車. Well, yes, it could be called that (next-generation streetcar), but readers and listeners are not given any hint as to what LRT stands for. This makes LRT a logogram for the Japanese expression 次世代型路面電車, and there is no chance of any significant number of native Japanese speakers ever learning what LRT actually stands for, nor will they think of anything but 次世代型路面電車 when they see or hear the Japanese logogram LRT. But that’s just fine, because LRT is Japanese.
I would advise English translators to gloss LRT with its expansion, and to never use SNS unless you are addressing or writing for an audience that would recognize it, and that is quite rare.