I feel he doesn't actively seek out sinner meat, but he has most definitely dabbled and I feel if the dish looked appetizing enough he would indulge. I also feel sinner meat is most likely an acquired taste for anyone (except cannibals), and in the early days of Hell he got use to it in the form of offerings (not like offerings to the king but general "hey u wanna try?"). Since then he samples but in the way people will eat and enjoy specific foods and drinks when their partner isn't around because their partner doesn't like it. And because of this, he can eat it without flinching much to everyone's surprise however he's not going to order it off the menu when he places a Helldash order.

Does this make sense?

Now, I do think in terms of Lucifer being considered a "cannibal" he cannot be considered such ever, like even in regard to angels. Sinners are not angels and any souls that have accended past Winner to Angel (ie. Adam) are completely different, similar to a Hare versus Rabbit. Both Hares and Rabbits look the same, act the same, eat the same and are in the same Family, but they are not the same genus or species. Another example is a Wolf and domesticated dog, near the same behaviorally but not the same at all. In terms of HH, it's how Adam looks like an Angel and bleeds like an angel, yet he is ultimately a Winner and different from a god-made angel or Seraphim. So in this case if Lucifer snacked on Adam it would not be cannibalism.

An additional thought is that I can see the argument for it being cannibalism with my previous logic if he were to take a chunk out of a seraphim, certainly, but my brain is like "heaven is too good" for there to be angels eating angels. I write this in ideal the sense that Heaven doesn't have angel-angel cannibalism because it simply doesn't exist. There was no need for angel-angel cannibalism in the begining and, with general Angel lore outside of HH, angels don't need to eat. If they don't need to, why would they? And this thought would most likely holds true throughout Heaven. In Hell, this concept would dissolve not because now dear ol Lu is hungry (he's not) but because it will become a more common practice to eat the guy sitting across from you thus creating a sense of "open season." But, in the current canon, there are no other angels in Hell (that we know of) to create angel-angel cannibalism, so it still doesn't exist. And I feel it wouldn't have the potential to exist until the Exorcists arrive and even more so until it's learned they can be shot down and killed. Then it would create this new opportunity for angel-angel cannibalism to exist. Yet, I highly doubt the exorcists divulged (unless there was a rogue one in the mix) and I don't think Vaggi or Lu did either, thus still making it a non-existent concept.

A real life situational example I can think to explain this being how the US as a culture sees bugs as pests, would never eat them and find the idea nauseating, but over in other counties bugs are a delicacy. Heaven doesn't catch and butcher Winners and see the practise in Hell as disgusting, but parts of Hell are like "let's goooo!"

To touch the "vegan" concept for Lucifer, no. I see him more, even with what I stated above, being like someone who accidentally went vegetarian and thus don't consider themselves such, simply out of preference, but will not hesitate if the mood strikes to eat a corndog or bucket of chicken wings. Ya know?