Switch 2 will be backwards compatible with Switch

Unfortunately it looks like they will again use a very outdated SoC, likely one that doesn't even match a several years old Steam Deck. Probably an 8nm chip, based on Nvidia's outdated Ampere architecture. See e.g. here https://www.reddit.com/r/GamingLeaksAndRumours/comments/1fjy...

Which would mean the SoC is even more outdated than the Switch 1 SoC was at launch. Reason is probably that Nintendo originally wanted to release the new hardware significantly earlier.

I really don't understand why they are planning those chips apparently many years in advance, when some other manufacturer (AMD, Qualcomm, Intel, MediaTek) could have supplied a more modern SoC without many modifications in a relatively short timeframe at a better price than Nvidia.

This would have made backwards compatibility more difficult, but I don't think this is that big of an issue anyway. Nintendo often didn't have it in the past, and few people complained. After all, old games can still be played on the old hardware.

Having a modern SoC isn't a priority for Nintendo or the vast majority of their customers.

The fact that the Switch 1 SoC is so outdated now is the main reason the console is replaced with a Switch 2. E.g. there a fewer and fewer cross-platform releases that come to the Switch. So having an outdated SoC means shaving of years of the console's potential life span.