I'm searching for backup eShop content under version 4.x.
And I found this in tutorial section:How to Dump and Backup eShop Games and DLC
Luckily I found this post is extremely useful and now I have successfully finished the process of download->decrypt->make.3ds/.cia of those free 3ds games...
btw i feel this a good time to remind you guys that sea of thieves was made by rare, who also made DKC1-3 and DK64, alongside banjo kazooie and conker's bad fur day