Do you know if this persists across system updates?It's a 3rd party tool named MisakaX. No jailbreak required to enable this. Took 5 minutes to download the 3rd party tool on my desktop computer, fetch the config file from the iPad Mini, edit the config file and then reboot my iPad Mini. It's not some crazy hack or sketch jailbreak - its modifying a file that flags if a iPad has access to Stage Manager or not.
Upon reboot - I have full on Stage Manager. It is a very nice feature to have.