I would guess the 3DS is far more "jailbroken" than the switch.

Jailbroken 3DS scene is usually for modding the console OS itself given how easy it is to run custom firmware. And for ports, and emulation. While the GBA has a pretty dedicated community for custom games and romhacks, people often create games for the platform at gamejams because of how great the dev tooling is. It's a bit lackluster on the 3DS, but I did find the Love Brew[0] framework to be really nice. Even has simulator support[1] for testing your builds locally, though fonts will look much different on real hardware, with likely a bunch of other gotchas. Running out of RAM being a big one.

[0] https://lovebrew.org/

[1] https://github.com/lovebrew/nest

edit: compared it to the GBA homebrew scene since it's a large dedicated community to derive pros and cons between the two from. Switch is still receiving updates from Nintendo to brick your system.

It is. Any 3DS can be jailbroken with CFW with a simple Internet guide and no physical modifications. As far as I know, the Switch CFW is locked to only V1 motherboards or modchips, making it far less accessible even if it is more powerful.