Add your own Game to the PlayStation Classic using a USB Flash Drive: Spiderman - YouTube
Modding the 2nd USB port for more current : r/PlaystationClassic
PlayStation Classic - Mod My Classic Wiki
PlayStation Classic Hacking: You can now load any PS1 game you please through a USB pen drive! (without even modding your console's files) - Wololo.net
How to Hack the PlayStation Classic with Bleemsync | Retronauts
Hacking an SSD in a Playstation Classic - Retro Gaming Projects - Tweakblogs - Tweakers