Learn Italian: Il nomade lavora con ciò che lo tiene connesso. - The nomad works with what keeps him connected.

Ciò che literally means 'that which'. You use it when 'what' is not a question word, but rather stands in for a thing or concept in the middle of a statement. You could also perfectly replace it with quello che here.

How would we rephrase this sentence using the impersonal si to mean 'One works with what keeps one connected'?

You would say: Si lavora con ciò che ci tiene connessi. Notice two things: we use ci as the object pronoun for an impersonal sentence (literally 'keeps us'), and because of this impersonal structure, the adjective must be plural. This is why connesso changes to connessi, which relies on the exact same plural adjective rule you are learning for si è!

Why does the pronoun lo come before the verb tiene?

Lo is a direct object pronoun meaning 'him'. Unlike in English, Italian object pronouns are placed immediately before the conjugated verb. So, 'keeps him' becomes lo tiene.

Is tenere always the right verb for 'to keep'?

It is the best choice when 'to keep' means to maintain someone or something in a certain physical or mental state (like keeping someone connected, keeping a door open, or keeping a drink cold). However, if you mean 'to keep doing something', you would use continuare a instead.