I'm a foreign scientist at LANL, working only on open (non-clearance) science, and I'm leaving my scientist 2 job (early career 'permanent' position, right after post-doc) for a tenure track in academia. Most of my early-career friends (foreign or US, 6 of the 7 early career friends I have here) are leaving or making concrete plans to leave, either to industry or to academia. The main reason for that is that it is very difficult at LANL to work only on open science, especially as an early-career scientist. Scientist positions at LANL are soft money, meaning you must find your own funding (for all 12 months of the year, as opposed to just 3 in universities). I would absolutely advise someone to come as a postdoc, just not so much to stay on as a scientist. I am leaving in good terms and will keep strong collaborations with LANL folks, but in my opinion it's very clear that any tenure track (in the US or not) is vastly better than a scientist position at LANL.