1. You have to update the firmware to current version after a factory reset.
Download links can be found here:
https://pgaskin.net/KoboStuff/kobofirmware.html
At the time of this post, the current version for Libra 2 is is:
https://kbdownload1-a.akamaihd.net/f...4.34.20097.zip
2. Once the Firwmare is up to date, connect the Kobo to a PC, edit your KOBOeReader/.kobo/Kobo/Kobo eReader.conf file. in the [ApplicationPreferences] section, add a line that says "SideloadedMode=true" (without quotes.) If the PC is Windows, you need to use a text editor that will respect and keep the Unix New Line convention. (Notepad++ is usually the suggested go to for people to install on a Windows PC.)
3. Eject the Kobo, then power off and restart, you will be in Sideload mode.