I've had problems with my ios 9 jailbreak and wish I could've came across this sooner because I have been waiting so long for this ios 10 jailbreak. Today I restored through my settings while jailbroken(long story as to why, dont ask) and I hunted down and found this method and saved myself and anyone who is reading a loss of their JB. THIS WILL WORK. I was tweaking with all my files and mTerminal all day making more problems and this cleared all of them in about 10 minutes!! THIS IS ALSO A GOOD METHOD IF YOU WANT TO CLEAN UP YOUR JUNKED UP IDEVICE/MAKE SURE YOU HAVE ALL REQUIREMENTS FIRST
Requirements Your iDevice and a computer, Cydia Fix (lib.zip), iFile (if you dont have an ifile loaded already I will be uploading an ipa soon to follow the steps/if you have ifile skip Step 2), Cydia Impactor, iFunBox
Alright, let's get started. Also please note, you must be running in jailbroken mode through the entire process
Step 1 - Download all the things from the required list.
Step 2 - Sideload the iFile IPA using Cydia Impactor onto your phone (just drag the iFile 2.ipa into the Impactor window)
Step 3 - Install iFunBox, connect your phone to the computer, unzip the Cydia Fix.zip and then drag the lib folder into the tab called iBooks.
Step 4 - Open iFile on your iDevice and navigate to /User/Media/Books. Click on edit in the top right corner then press the lib folder. Press the clipboard icon in the bottom right and then press cut. Now navigate to /var (if you navigate all the way back it should be in the list there) then press Edit, press the same clipboard icon then paste.
Step 5 - Reboot your phone and jailbreak again.
Step 6 - Open up Cydia and try to install Cydia Substrate, if it works you should be all set and done. If it gives you this error, keep reading.
Step 7 - Download Mobile Terminal from [here](http://files11.thebigboss.org/repofiles/cydia/debs2.0/mterminal_1.3-2.deb) (you will have to sign it yourself using the iOS Signer Tool, download it from here. Sideload the IPA you just made using Cydia Impactor (I know it says without in the title but if you get this error you will need it. Don't worry if it didn't work before doing the other steps, it will now).
Step 8 - Open up the Terminal application on your phone and do the command "su", now you need to write in your root password but the default should be "alpine" (you won't see the characters but it's writing either way).
Step 9 - Now when you have root in Terminal run this command "rm -f /Library/MobileSubstrate/DynamicLibraries" then try installing Mobile Substrate again. Shouldn't be a problem this time.
DONE. Please reply for help/ an issue with the post (yes, I got the method from Reddit just trying to help out)