You have to keep in mind that attenuation and absorption are not to be used interchangeably!
As Tetsujin states in their comment, the foam won't do much, as it may attenuate the sound in a "statistical manner". This means that the sound will have to interact with the material for quite some time but what you are interested in is to block the sound ...
I'm just going to evaluate the options you mention.
covering surfaces with blankets, duvets, or comforters
Not really a professional option and can actually cause bad results
covering surfaces with "acoustic geo textile" (literal translation from Portuguese, product here) with 5mm, 10mm or 20mm thickness
You can't really do much with 20mm ...