Social Network Accounts Owned by the Same Person
Solution 1:
Sometimes called a sock puppet account. Lexico has
2 A false online identity, typically created by a person or group in order to promote their own opinions or views.
Sock puppets are banned in many online venues.
These bloggers marshaled their legion of sock puppets to engage in intellectual combat.
Solution 2:
Also, alternate account, or “alt”. Wiktionary has:
(Internet, gaming) An alternate or secondary character.
1996, "Jonobie D. Baker", Survey of MUSHers. (on newsgroup rec.games.mud.tiny)
Of these alts, how many of them are a gender other than your own?
2000, "KaVir", Code Bases - why release buggy crap? (on newsgroup alt.mud)
Yes, I have many alts, and no, none of the others have any unusual capitalisation.
(Internet) An alternate account.
Solution 3:
They are certainly not bots. As this Wkipedia article explains a bot is either completely or largely automated and is used to make a certain product or point of view look more popular than it actually is. Someone with more than one account on a given social media platform is still, usually, managing the accounts manually. There might be a certain amount of copying and pasting going on but the process is usually manual.
The accounts could be described as duplicate accounts although this term is usually applied to accounts with businesses or official entities which have been created in error. @RobJarvis suggests "alias account" which is good since alias is defined by Lexico as
a false or assumed identity.
Quite often aliases are adopted for nefarious reasons but some are legitimate, good examples being stage names of performers and pen names of writers. People working under stage or pen names are often better known by their pen name than by their real one.
In fact it is easy to imagine that a person famous under their pen name might well choose to have two social media accounts, one under their assumed name which is used to communicate with their fans and one under their 'real' or 'birth' name which is used to communicate with family and close friends.
Depending on the reason for having more than one account you can make a choice of term for an account which is not associated with the 'real' identity from alias account, duplicate account and false (or fake) account.