Libnah is mentioned in the Bible as a Shephelah town near the border of Gath, fortified in Hezekiah’s time, existing during the mid-9th, late 8th, and late 7th century BC.
Only Tel Erani, Tel Burna, and Tel Goded, may be viable candidates for this site, as far as I’m concerned. Of these, I have my doubts Tel ‘Erani was inhabited in the 9th century (Late Iron IIA), and, while there are Iron IIa remains at Goded, the Bliss excavation surprisingly did not find evidence of pre-Selucian fortification, though Goded is certainly of greater importance than Burna, though I doubt it could secede.
Tell el-Beidah is more likely Achzib (the lmlk pottery???), and, even though its name is suggestive of Libnah, it is as of yet untested archaeologically, though, if Azekah was Gittite (which will be confirmed or denied in the upcoming excavations), this certainly would be a plausible option.