The Print Service plugin supports printers that support MOPRIA.
It isn't related to Mobile Print, which is a server based print application
The 3020 can't do MOPRIA so the plugin won't work, you would need to buy something like the WPSA-100 to get MOPRIA.
It's possible to print from iOS because Airprint is covered by the printer.
Airprint and MOPRIA are nearly identical, but they didn't come out at the same time and are not exactly the same.
So when this printer came out originally, it didn't support MOPRIA, it just did Airprint.
By the time MOPRIA came out, Xerox sold newer devices with the ability, they didn't give it away to older models, they just released new models with the feature.
The only way to print from Android to this specific printer would be Google Cloudprint. Which is another thing entirely.
Thank you for this explanation. Is it possible to add MOPRIA with firmware updete? If it is possible, what are the chances this to happened?
It would be possible, it hasn't happened and almost certainly won't. There is no money in making an older device as good as the new models.
Xerox has a thing called a FER (Feature Enhancement Request), if you have a Service agreement you can call the support line and request a FER to get MOPRIA, if you don't have an agreement you can't get one. But it is considered a suggestion, not a guarantee, if enough paying customers demand it, it could happen.