Nintendo gave us an alternative use for your gold coins:
https://gonintendo.com/stories/318313-my-nintendo-gold-points-can-be-used-to-purchase-a-switch-online-m

Nice move of them.

Updated the OP further, thanks :)

And they will still be worth a few cents. It's logical since gold coins can be used on the eShop, and the membership can be bought through there... Are those NES controllers also bought through the eShop?

https://gonintendo.com/stories/318313-my-nintendo-gold-points-can-be-used-to-purchase-a-switch-online-m

NSO requirement depends on the developer/publisher. Jackbox just said it's not needed for their games.
https://nintendoeverything.com/jackbox-games-releases-wont-require-nintendo-switch-online-subscription/

If the game host its own servers, you don't need the NSO requirement???

And.... NSO is online and the update is LIVE
This morning I did not perform the OS update, and online still worked for Splatoon 2 and Rocket League.
There could be a temporary period when it works... or they can't control the online when people are below OS6.

Here's some additional update info:

Nintendo Switch Online* features and functionality have been added, including:

• Save Data Cloud Backup
  • User your internet connection to back up game save data for compatible games
  • Some games are not compatible with Save Data Cloud
  • To back up save data or download a previous backup, head to System Settings > Data Management > Save Data Cloud Backup

  *Nintendo Switch Online membership (sold separately) and Nintendo Account required for online play. Not available in all countries. Internet access required for online features. Save Data Cloud backup available in compatible games. Terms apply. To learn more, click here.

Added the following system functionality

• Upload up to four Album screenshots at once on supported social network services
  • Only one captured video can be uploaded at once
• Select from six new Captain Toad icons for your user
  • To edit your user icon, head to your My Page on the top left of the Home Menu > Profile
• Play your digital software and content on non-primary consoles by linking your Nintendo Account
  • The term “active console” has been renamed “primary console” in Nintendo eShops
  • Playing software in multiple consoles has certain restrictions
• Display of Nintendo Switch News articles will be limited to match the restricted software parental controls setting selections
  • Please note that the restriction will only apply to News articles distributed after the release of version 6.0.0.
• Change the layout of the USB keyboard to the desired language
  • To change the language, head to the System Settings > System > USB Keyboard

Removed the following system functionality

• After installing the system update, it will no longer be possible to unlink your Nintendo Account from your Nintendo Switch user

General system stability improvements to enhance the user’s experience, including:

• Compatibility improvements have been made for a controller licensed by Nintendo