Developer Jacques Gagnon aka Darthcloud has just gotten the Switch Online N64 controller working with original N64 hardware via his Blue Retro platform: An open source project (under the CERN-OHL-P-2.0 & Apache-2.0 licenses respectively) that uses an ESP32 chip to provide a low-latency bluetooth-to-console adapter. It’s still in DIY form, but if interest is high enough, maybe it’ll become a manufactured product, like the PSRetroUno!?
Build your own N64 Blue Retro Adapter: https://github.com/darthcloud/BlueRetro/wiki/BlueRetro-DIY-Build-Instructions / https://github.com/darthcloud/BlueRetro/wiki/BlueRetro-Cables-Build-Instructions#nintendo-64-adapter-cable
Switch Online Controllers: https://www.retrorgb.com/switch-online-genesis-n64-controllers-now-available-to-purchase.html
I’ve only spent a few minutes with the N64 Switch online controller, but it seems true to the original, with a built-in rumble pack and that classic “trident” feel. There’s no support for a Controller Pak / Memory Card, but not all games require it. It also seems that Nintendo is listening to fans’ enthusiasm for the controller, as they’ve been adding support for it in Switch games – Maybe this means they’ll manufacture more and have enough stock for everyone? If you’re an N64 fan, fingers crossed.