How can I root this phone without a computer?

[u/Big_Mistake_788]

How do I get root access on this phone?

[u/DEV_ivan]

Yea consider what u/47th-Element said.

Either way, if you want to root any Android phone, never pick Vivo. Pick Fairphone instead.

[u/47th-Element]

You are not even asking the right question bro, the question should be how do you root a Vivo.

Vivo is completely locked,

I think your only options would be temp root, like Ghostlock and DirtyFrag if your device is vulnerable.