I think I've managed to guesstimate the dates for most of the non-canon BlackThorne comics
BattleTech #3 and BattleTech Annual: 2789 (Early 1st Succession War)
Justification: The ship that delivers the Lyran lance to investigate Mozirje is at least 50 times the size of the DropShip and was able to move from the jump point to orbit. To me, that says WarShip. The early 1st Succession War was the last time any Great House had enough of a WarShip fleet to dispatch one as an escort for a recon lance. It also makes sense that the DCMS research base seemed to have plenty of LAMs for defense, since those would have been more common back then, too. Also, it's much more likely that the Combine would be dabbling in genetic engineering and mega-cybernetics at the tail end of 150 years of relative peace and scientific advancement, rather than doing so after 300+ years of technological decline. (Plus, Combine scientists were the ones that mutated a Vodnik into a Toorima and released the resulting man-eating monster beastie into the sewers of Solaris City, so the interest in that sort of research is demonstrably there, once the technology is available.)
BattleTech 3-D #1: 2896
Justification: The intro says the setting (Frazer) has been a stronghold of the Federated Suns for 30 years of uninterrupted war. Frazer fell to the Federated Suns sometime in the 2nd Succession War. Thus, 2896 is the first subsequent opportunity to mark 30 years of uninterrupted war during which the Federated Suns had control of Frazer - dating from the start of the 3rd Succession War in 2866.
BattleForce #1 and #2: 3015
Justification: There's a strange notation at the start of the story identifying it as 3015 (albeit immeidately following that with the confusing "Currently 3025"). I take that to mean the story takes place in 3015, but the BattleTech game universe, at the time, had a "now" of 3025, indicating this was taking place in the past rather than moving the timeline forward. 3015 is right when Hanse and Michael were scheming against each other, so the chronology fits. (Though the worries that this could trigger a new war is somewhat nonsensical and better fits the 3026-3027 timeframe, in the brief interbellum period.)
BattleTech #4: 3024
Justification: It's an adaptation of a scenario, and the various TRO materials referring to that event place it in 3024
BattleTech #1 & BattleTech #2: 3025
Justification: It features a Hatchetman, which had its first recorded battle in 3025.
BattleTech #5 and BattleTech #6: 3026
Justification: All the elements noted in the 3025 House sourcebooks (the Canopian/Andurien alliance, etc.) are present and treated as current, so it can be assumed to be building off those foundations.