Is selling services to increase Instagram followers—whether they are real, Arab, or foreign dummy accounts—with the buyer's full knowledge and consent regarding their type, permissible or forbidden (halal or haram)?

Selling fake followers is absolutely impermissible because it aids in deception and fraud, making the account holder appear to have what they do not. The buyer, knowing they are fake, does not validate the transaction. As for selling accounts with real followers, it is permissible as long as it is not highly probable that the buyer intends it for a bad purpose, due to Allah's saying: (And cooperate in righteousness and piety, but do not cooperate in sin and aggression). Buying fake followers is forgery, an adornment of falsehood and lies, and a deception to buyers and advertisers. However, increasing the number of real followers to spread benefit is not blameworthy if the intention is sincere and aimed at pleasing Allah and benefiting Muslims. But if the intention is to gain prestige, status, and fame, then it is reprehensible and forbidden.