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It's child's play on the SRAM non-hydro levers. I have not tried on hydro but it looks to be mostly the same process: https://jeffsbike.blogspot.com/2020/05/curing-1x-sram-1x-to-2x-shifting.html?m=1
If the bike you're referring to is this one, then it looks it doesn't have a left shifter paddle so you'd have to source that somewhere
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The drop bar levers on the market are actually pretty nice nowadays, you can use them from the hood or drops. I think you can get ones from fox, Easton, enve, pro, wolf tooth and probably more
https://www.biketart.com/products/pro-discover-dropper-seatpost-dropbar-lever?variant=42485105262771
I believe it's an older SRAM Force mechanical/hydro unit - stock on the 1x Slate.