There's a memory card exploit that lets you load games from ISOs, either from a hard drive or the network card via SMB share. No patching or burning required. Does not work for PS1 titles however.
Also from USB, unfortunately it's only USB 1.1 so titles with FMV sequence tend to stutter, so for slim models the network SMB share it's preferred...
About PS1 titles, there is a Sony PS1 emulator for PS2 called POPS that you can use with OPL but from what I read it has not a wide compatibility and it's not officially distributed by Sony, the other option is to use mechapwn to boot PS1 CDs, but it doesn't work on the early PS2 models according to this: https://github.com/MechaResearch/MechaPwn?tab=readme-ov-file...
There's also the MX4SIO adapter for loading games from a microSD card. It doesn't work with all titles and may have some stutters but I've had pretty good luck with it.
