The only version available for the Nintendo Switch is "The Complete Adventure" physically, it is no longer on the eShop as of June 25th, 2019. S1 & S2 episodes come pre-installed.
Here is a good guide to hack your switch (Make sure to remove the web.archive.org part of the link when going on Github pages). Here is a guide to load Switch games.
Get the games at nxbrew.com or nsw2u.com, and make sure to use an adblocker. Use a hacked/modchipped Switch to boot the .xci or .nsp file. The method I recommend is via Tinfoil. S2 episodes come pre-installed, which will save you downloading the episodes.
Warning! You probably know this already, but having a hacked Switch may get it banned from accessing the internet and Nintendo’s servers if you do not have the default.txt in atmosphere/hosts and the exosphere.ini on the root. I’d recommend keeping all your hacked stuff on your emuMMC and your legit stuff on your sysMMC. If you have a patched/OLED Switch, you can put in a modchip, but you need some soldering experience and you risk bricking your Switch.
Download from nxbrew
Download from nsw2u