The Switch runs on a modified Tegra X1 chip, vastly underpowered compared to a gaming PC or the PS4/Xbox One. Larian performed miracles to make it work:
If you have found a Divinity Original Sin 2 Definitive Edition [01008A600A0C8000][v0].nsp file online, here is how it fits into the Switch ecosystem:
If you have legally dumped your own cartridge and are facing install errors: