I remember when the 3DS was region locked (cartridges can only be read if the console is bought in the same country those games are from) meaning it’s a headache having to switch between two variants of the handheld (I had a Japanese 3DS XL and an American 3DS regular back then, alternating on each one depending on which game I wanted to play). The switch alleviated this by making the cartridges / console region free.
For stuff like the SNES it wasn’t a big deal. just open the console. cut out the plastic peg and you’re playing Japanese SNES games. a grade school friend of mine at the time showed me this. His Dad travelled to Japan for business all the time and would bring back SNES games for him. His dad tried playing the games in the US SNES but noticed that the games wouldn’t slide in correctly. then he saw that on US SNES cartridges there was a notch in all the cartridge cases while the Japanese cartridges didn’t have this notch. Looked inside the console and sure enough there’s a plastic peg sticking out that lined up with the US cartridges. so he figured “what if I remove the peg?” sure enough once the peg was cut out the US SNES could play Japanese SNES games. That was Nintendos region lock prevention, a plastic peg.
For the PS1 a local comic shop was selling chips for it. bought a chip, my dad took the PS1 and chip into work with him one day and got his buddy to solder it in for me. worked like a charm.
For the PS2 I just ended up importing a translucent blue PS2 from Japan. it was just easier that way.
For the Dreamcast literally just had to get a boot disc and you were good to go.
I remember I had to use an adapter to play US games on my PAL SNES to bypass the security chip. So the adapter has two slots one for the PAL Snes game for the security check and the other for the US or JP game you want to play.