Well, I did mention Flashify does not work on newer operating systems.
I don't know of any way to install TWRP without a PC. But what happened to your PC? Why can't you use that to flash either TWRP or the ROM itself?
Flashing ROMs without a PC is possible, either with TWRP (but you have to either boot into it or flash it permanently; and you can't do either one of them without a computer), or with an SD Card and existing PE Recovery. Your device doesn't have an SD Card slot? Or you just don't have any laying around?