One thing I wish there was more visibility of is "is this device still getting security updates", because there's often almost no visibility about that (and while you obviously can't say the vendor won't fix future vulnerabilities, you can say whether the vendor has fixed all known vulnerabilities), even online, yet alone anything pushed to the device to let its user know it is no longer secure.
e.g., http://web.archive.org/web/20161224231459/https://wiki.cyano... is the old CyanogenMod wiki page for the Galaxy S2: the last "development channel" (i.e., unstable) build is 2016-12-18, the last "release channel" (i.e., stable) build is 2015-11-16. There is nothing on the device page to suggest the stable build is known to be insecure (though given the number of Android bugs found in the last year unquestionably is!), yet alone anything about upstream vendors dropping support for the device and the unstable build being known to be insecure too. How is LineageOS going to do better than that? That's a damn low bar.