You don't need a permanent residence, but to use PIX you have to get an ID called CPF. This is your IRS number, as you said, tax number. It's easy to get but it takes time, you can have one as national from different country.

This is true but the next step is a Brazilian bank account.

OK so it's firmly in the "not reasonable" territory for tourists. Just pay cash or credit card. Tourists aren't going to wait a while for a Brazilian tax id then use a Brazilian bank account before their trip. Just to select Pix as your payment method instead of card you already have in the Uber app.

This isnt a take down of Pix. Sounds excellent and should be replicated in other countries. Lets just not pretend its a viable solution for tourists.

There seems to be a new solution for tourists in Brazil to use Pix but with their digital wallet: https://www.infomoney.com.br/minhas-financas/pix-para-gringo...

Is there an online bank that allows to create an account just with the CPF and no proof of permanent residence?

I googled a bit, seems that maybe Bradesco bank allows it but it's a lot of paperwork and you need to be physically present at the bank branch.

I think remitly works

https://blog.remitly.com/money-transfer/complete-guide-brazi...

From what I understand it supports transferring money to an account identified by a Pix key. I don't see that you can get a Pix key there.

Similarly Revolut has an announcement but I don't believe it is available yet.

Banco Rendimento supports it, I believe.