PETROL BRASILEIROS SPON ADS EACH REP 2 ORD SHS-2616580
When looking at ADS’s (or other depository type interests/receipts such as ADR’s), the listing or trading of the actual ADS or ADR is irrelevant. All that matters is the qualifying status of the underlying shares. If the underlying shares are ISA qualifying (because they are listed on a recognised stock exchange or admitted to trading on a recognised stock exchange in the EEA, including the UK), then the ADS (or ADR) automatically qualify (regardless of its listing status).
According to the links below, evidence state the underlying stock (common shares) is listed on the on the B3 stock exchange in Brazil under ticker PETR3 therefore, on that basis, the ADR should qualify for stocks & shares ISA inclusion.
It looks as though B3 is the new trading name for the BM & F Bovespa (see link below).
The listing or trading of the actual ADR or ADS is irrelevant. All that matters is the qualifying status of the underlying shares.