I am going to say that it’s unethical for someone to eat others or themselves, lab grown or not, because the community members in a society want to 1) curtail or reduce suffering and 2) increase ways to promote better judgment and impulse controls.

1 - We treat cattle and animals for food production with such contempt and disdain and cruelty, and if we were to start eating humans (lab grown, self-eating or otherwise) we’ll treat humans the same. Delegating some humans to be eaten, lab grown (by choice or not) or otherwise, is going to create a lot of societal strife and suffering. How does self-eating contribute to suffering? See reason 2.

2 - People who consume others or themselves cannot be guaranteed to be devoid of sociopathic characteristics. Even if someone is just eating themselves, it blurs the line between food source and community member.

I think it is the same as people who smoke or cut themselves to relieve stress—yes, whatever you’re doing is your choice and seemingly only affecting you. However, the second hand smoke/scarring in the case of the self-cannibal is their poor judgment and poor impulse control. We expect society members to exercise better judgment and impulse control because the way they think impacts everyone around them.

Why does self-cannibalism seem like poor judgment? Think again of someone who cuts themselves to relieve stress. The way you treat your yourself, including your body, is a reflection of your state of mind. Only a narcissist would say that they’re in complete control of their mind, including the subconscious part, and so their self-eating will be harmless and not result in any bad behavior towards others, ever. We already know vegetarians have more empathy than meat eaters: https://www.psychologytoday.com/us/blog/animal-emotions/201207/brain-scans-show-vegetarians-more-empathic-omnivores

As mentioned, we have historically always treated animal sources of nutrition with disdain, contempt and cruelty. If someone feels that it’s okay for them to eat themselves using lab grown meat, I worry what kind of psychological interplay justifies that decision for them. Do they hate themselves? Is this self-harm? What will their interactions with other people be like after doing this?

So, yes autonomy and self-actualization is an inherent right of cognitively advanced beings. But they lose that right the second it starts impacting someone else’s self-actualization.

In short, even self-cannibalism is unethical because society wants members who are not sociopaths and who won’t contribute to the suffering of other members.