Chapter 84.1 <— click on the link to read it. Thanks to anonymous for the donation.
So what does Old John look like now?
During their first meeting, Old John was described as old and decrepit:
“It was an old mechanical puppet. They could hear its parts clanging at its every step. Though its appearance was worse than the one star mechanical puppets they had seen before, this one had five stars on its chest.”
However, after Xiu learned forging, he upgraded Old John and when Du Ze emerged from the wheel of time, he looked human:
“The Fire Phoenix tweeted then flew up and perched on the shoulder of someone who had appeared without Du Ze noticing him. It was a stranger with brown hair who looked very approachable.”
This time Xiu made a human-type mechanical puppet body for Old John. When Xiu finishes fixing Old John he will be a seven-star mechanical puppet, the highest that Xiu can make. We can tell from this that Xiu does value Old John a lot.
Since there is currently no description, we can imagine for ourselves what he looks like. I think Old John is like a bodyguard/butler so that image above is what I think he looks like now.