While following the guide on an old 3DS XL on version 11.17.0-50U, I ran into an issue during the "Installing boot9strap" section of the guide:

https://3ds.hacks.guide/installing-boot9strap-(mset9-cli)

While performing the sanity checks, I ran into the "Error 10: Database(s) malformed or missing!" error. The guide mentions this error and provides instructions, in the form of a series of screenshots, for fixing it:

https://3ds.hacks.guide/images/screenshots/database-reset.jpg

I tried following these instructions by going to System Settings -> Data Management -> Nintendo 3DS -> Software. However, I did not see the message shown on the right side of the image, and there was no Reset button.

The troubleshooting page contains some more information about this error:

https://3ds.hacks.guide/troubleshooting#installing-boot9strap-mset9

It says that the error can occur if you have never installed any eShop titles on the SD card. This was the case for me; I did the following:

1. Perform a system transfer away from this 3DS. All eShop titles were moved to the target system.
2. Power on the system and go through the initial setup screens.
3. Open System Settings and the eShop for the first time, in case they initialize anything.
4. Update the system to the latest version.
5. Attempt to follow the guide.

I found a workaround for this issue. Even though the eShop no longer allows you to buy games or download free games for the first time, it still allows you to download updates for games. So, I went to the eShop, used the filter to find free downloads (by setting the minimum and maximum prices to zero), and downloaded an update. You can download an update without having the corresponding game. After I did this, the error disappeared and I was able to follow the rest of the guide.

So, my suggestion is as follows: mention that if the Reset option shown in the image doesn't appear, then the workaround I described above might resolve the problem.