As far as my knowledge goes there were some helps from the government regarding rents but only if the tenant has special conditions regarding losses of income.
They were helped to pay the rents if they apply for help from a governmental department. (They would make a loan of the value of the rent to help tenants pay landlords, as there are many landlords for whom rents are their only form of income.)
The rules applied during «emergency State» periods and for what I have heard, not so many people asked for help because of all the papers/documents needed.
What happened in many cases - also mine - were that tenants and landlords talk to each other trying to find a way to do it the best way possible. No penalties for delays, some reductions in some periods, etc.
During the state of emergency period, it was also not possible to terminate contracts and a landlord cannot evict a tenant who doesn't pay rent.
In no case the rents were eliminated. They were just postponed.
State of emergency is no longer in place in Portugal.
I hope this helps you 🙂