Stagefright fixer updates are rolling our as an OTA for exactly three T-Mobile LG devices right now. You have LG G3 first, whose new build no. will be D85120g, while that for LG G Flex and LG G2 will be D95920t and D80130c.
The updates are very minor, especially when you’re hearing lots of Marshmallows around you.
You should know that T-Mobile has unveiled its Marshmallow update plans, and that includes LG G4, LG G3 and LG G Stylo already. The T-Mobile LG G Flex and Flex 2 should make it to the list too, but right there is no word available on it.
LG G2 is now more than 2 years old, and has thus been left out of Marshmallow update by LG and T-Mobile, and you can’t really blame them for this.
To check for the OTA update currently rolling out, head to Settings > About device, and check under system update.