so just thinking out loud here regarding lana sampling herself...
honestly i think the "sample" (if it is actually a sample and not just a callback/reference) will be from HBTB. was it BOZ or eclipse who referenced it at one point and suggested it would make sense/be significant later? and i do think HBTB is kind of a fan fave, even though it's not a personal fave of mine. i also think there's a lot to work with there: the outro vocalisations, the spoken word ending (it could potentially be used in the same way that the spoken word extract from Carnival of Souls is used in the 13 Beaches intro), the one line that all fans tend to go feral for ("you could be a bad motherfucker but that don't make you a man" - would also make sense w/ the whole 'fan favourite' thing), the distorted vocals that come in at the start of the track, any part of the instrumental, the "lights camera accion" part which would make a really cool sample, even the helicopter noise... there's a lot of possibilities. to me it just makes the most sense.
i don't think the sample will be from Video Games - yea it's lana's breakout hit and i'm sure we all have a place in our heart for it, but most fans don't really rate it that highly tbh (although it's literally my fave song of all time!).
God Knows I Tried is unlikely - this song was sooo slept on during HM's release and still is now tbh.