How to download screenshots after Miiverse closure

The most recent version of SmileBASIC takes a screenshot by pressing SELECT, and you can find the captures on the 3DS's SD on DCIM folder. However, the screenshots are compressed on .jpg image format, so it will have a lot of artifacs. If you have CFW, you can take a high quality screenshot with LumaCFW.

Here is the bad news. Anything you had on MiiVerse has been deleted for over a year now. There is no generic screenshot facility on the 3DS now. Now for the good news. A recent (June 2018) SmileBasic update added a screen shot function. Just hold down the select button for a bit. You should see a circular processing symbol. Then go to photos on your 3ds and you should see a picture for the top screen and another of the bottom. To get your pictures on your PC, fully power down the 3ds, remove the memory card and put it in your PC's memory card slot (if you don't have one you will have to buy a memory card reader add on). Then just find it in the DCIM folder and copy it where you please. Remember to put the memory card back in the 3ds when you are finished. This allows smilebasic screen grabs only of course.

Actually, a few months ago, somebody released a Miiverse Archive with something like 17 TB of user data. As long as you posted whatever screenshots you’re looking for to miiverse, then you should be able to find and download them at the archive. Here’s the American SmileBASIC Miiverse community