Artboard Snapping is broken when creating a new artboard
If you're creating a new artboard, you can snap the edges of the artboard to previously created artboards.
However, if you hold SHIFT to constrain proportions (handy if you're making social size assets for example), the snapping no longer works, even though you'll still see the snapping points.
Furthermore, when you constrain proportions, the artboard location will be a decimal point, meaning if you Export For Screens, you'll get extra pixels added to your artboard thanks to a different unrelated illustrator bug.
AI version 27.5
MacOS Ventura 13.2.1
I confirm that.
The workaround I use is to create a rectangle instead (it snaps to a vertical smart guide just fine with Shift held) and use Object > Artboards > Convert to Artboards command (I have it assigned to a hotkey)
But if artboards just worked — I’d perhaps used the dedicated tool, yeah.