Lightspeed Tokens: buyer beware!

What a load of rubbish. Dark trooper is much older than DTMG, and a couple of my guild mates used it on DT.

I think support are idiots as well, the reason DTMG wouldn’t be eligible is because he’s a conquest character.

Even if you already have him unlocked, he’d be excluded from the LSTs because it might be too much hassle to exclude a unit from LST activation but not upgrading.

Support are talking rubbish. You can’t use it on DTMG because he’s a conquest unit and they’re excluded from LSTs

If you tap/click on the i next to requirements, it opens a list of not allowed toons.
DT Gideon is/was a conquest toon and it clearly says "can't apply to conquest units"

Is the information in game? Yes
Is this information displayed well? No.
Do you also need to know what toons belong in each of the disallowed categories? Yes
Do you need to hunt for the info? Yes
Could CG have done better? Yes

Best part is I had to google to even find out what "Legacy Era" is.

Given the limitations on them & the low levels of the free one's they have zero value to me, as a whole they come across as something closer to "click bait" than an actual item anyone should be purchasing.

if you tap/click on the token it shows you what characters you have that are eligible for the token to be used on. Maybe next time be sure to take a good look at what you're buying before going through with it.

I disagree completely. 

1. Information is included in the game and it is readily accessible.
2. It's hardly the first time in SWGOH that you're supposed to tap "i" for more detailed information. We click on more info on store packs, on units, on abilities, on gear pieces, on datacrons, on raid tiers, on conquest node modifiers. 
3. There was a forum post with detailed information, including which characters are not eligible for LSTs.
4. In-game mail includes a link to the forums, directing players who want more detailed information towards that information. 
5. This is the 2nd round of LSTs, and these threads about LSTs were also posted several weeks ago, asking the same questions.

OP's problem is that they can't read. There was no deception or fault on CG's part here. 

Top left corner in the character screen has a clickable icon that shows which Era a given unit belongs to. 

I wish the Legacy Eras would be named, instead of just naming the recent ones

There's one Legacy Era: it's everything before the Era of Apprentices.

I did successfully use mine on original flavor Moff Gideon.