This is not only for CPLP countries (Brazil etc). Basically anyone from any country who can legally enter Portugal on a Schengen tourist visa, can on the very next day, apply for NIF, social security, get accommodation, work contract (any work, not highly qualified activity or anything). They can then file an expression of interest, legally stay, work, pay taxes in Portugal. Biometrics appointment takes ~2 years of waiting, following which they get their first temporary residence permit. Same workflow as described by @live2learn.
This was accomplished by amendments to Article 88 and 89 of the Aliens Act in 2017 which waived the requirement for a residence visa or job seeker’s visa to file an expression of interest.
Plenty of South Asians have emigrated via this route. I’ve talked to 4-5 people in Lisbon and Faro who are driving Ubers , working at restaurants, owning restaurants. They’ve all got the same story. Asked how they felt about SEF delays, none were particularly bothered - they like the fact that you can legal working immigrant status quickly with minimum fuss, and will eventually get European passports, intermediate delays don’t signify. They like the country, the weather and cost of living (compared to the rest of EU), and were generally appreciative of government support. (Small sample, anecdotal value only)
I agree with @live2learn, the date considered is likely to be the expression of interest date. What that maps to for ARI is still unclear, but if the spirit of the legislation is honoured, it is likely to be the ‘analysis’ date when the first fee was paid.