Since I am a forum administrator, I'm allowed to respond to a thread that is marked as closed. 
(Uma versão em português segue abaixo.)
I wanted to share the good news that @pmoreira on this other thread
managed to make progress getting Registro.BR to list the governmental domains at UF-level on the Public Suffix List.
According to @cpu's estimate, the change should take effect for Let's Encrypt around June 22. After it does, it should be possible to get a much larger number of certificates for domains at the municipality level.
There are still rate limits that will exist
However, the certificates per registered domain limit will be calculated at the municipality level, instead of at the UF level, once this change takes effect.