Do you tax on material weight ? But bigger sized systems tends to be easier to repair/recycle than nano electronics. They also often last longer.
Do you tax on raw materials ? That would exclude all the junk made abroad. Or on components ? That would make a gigantic and perpetually changing list to maintain, creating an incentive to always create alternatives only needed to game this tax.
Hope does that address the externality “not infinite material rarefaction” ? Making thinks more expensive just make them less affordable for a part of the population while the other part can not care much especially for cheap disposable(!) small devices.
I don’t have the perfect solution but IMHO we need regulations, not tax. Creating an obligatory (long) warranty would push the society in the sustainability direction. I don’t need 2$ led lamp, an even slimmer keyboard or a 120hz screen, just want it to last way more (or being able to make repair) that 2/3 product cycle time frame defined by the corp business team. Who want to say to their children “enjoy this tech while there’s still some rare earth left” ?