Perhaps look at this thread but suggest only follow Method 2 by coderus, https://talk.maemo.org/showpost.php?...80&postcount=5 although this pre-supposes that you have installed https://openrepos.net/content/ancelad/n9-repomirror to allow developer mode to be enabled.

If you peruse the forum you will find that there are now problems sourcing firmware appropriate to your particular product code, should you want to re-flash device in case of possible data corruption and sometimes compromise has too be made as you can't downgrade (but that's another story).