iPhone 11 A2111 compatibility with LTE bands in Europe (Portugal)
The modem and antenna setup in recent iPhones can't handle all of the band options at once, so Apple has split its models into devices that work with certain bands needed in the US and Canada, and devices that work with bands needed elsewhere.

The hardware of the models is pretty much the same, except that they have different modems that cover different LTE bands. Therefore, the phone you buy overseas or from black markets might not work properly on your current carrier. 

iPhone 11 A2111, 11 Pro A2160, and 11 Pro Max A2161 are the US/Canadian models. iPhone 11 A2221, 11 Pro A2215, and 11 Pro Max A2218 are the world models. iPhone 11 A2223, 11 Pro A2217, and 11 Pro Max A2220 are Chinese models.

Especially in Europe, the US models will get poorer coverage and speeds than the world models will. 

So it might work but not up to the expectancy level. I wouldn't suggest going with A2111 as Apple has provided the list of supporting bands. You can look for iPhone 11 A2221. 

https://www.apple.com/lae/iphone/LTE/#iphone-11