Navy one kind of was the standard one. More Navy Lynxes were built since it had far more export success than the Army Lynx. The latter was only operated by us and the Qatari Police.
And at the end of the day; throughout the world AS.12 has primarily been operated as a Naval missile, with the RN being the only British military service to do so (saw service on Wasp HAS.1, and Wessex HU.5). But it was considered a legacy 1960s system when Lynx was entering service in the late 1970s: the RN intended to have Sea Skua operational when Lynx reached IOC - AS.12 on HAS.2 was likely just backfilling the capability or simply helping to certify it for the French and other potential foreign customers. The UK’s ambition was to export both Navy Lynx and Sea Skua together.
The AAC appears to have had equally forward-looking requirement to replace AS.11 and only considered Hawkswing, HOT and TOW (and possibly Milan), that were in development at the time as air-launched ATGMs. So for Lynx AH.1 its only military customer evidently has no interest in trying AS.12 which was basically just a bigger AS.11.
However, the AS.12 mounting on both the RN and French HAS.2 appears to be the same “NATO flange” (sic) installation that the Hawkswing used to mount on AH.1 in the above video. So I imagine it technically could be adapted for AS.12 with compatible sights and control systems installed.
There’s the snippet from Flight International from the 1970s when Lynx was still in development and first being marketed for export, which doesn’t discern between Army Lynx and Navy Lynx in terms of weapon options. So maybe where some of the more exotic loadouts you mention come from, along with the stuff shown in this video from the 1980s or so, that seems to be geared towards (unsuccessfully) marketing Army Lynx abroad
