[Aachen]

I don't have time for an elaborate sourced answer but in short, yes, the efficiency gains of modern devices is almost negligible compared to the CO2e of producing a new device at current device lifespans. I can't remember if you would have to use a device for 15 or 25 years before upgrading is better than continuing to use it, but I thought it was 25

Edit: yes, 25. Found my go-to reference for this quickly after all

> The report about the cost of planned obsolescence by the European Environmental Bureau [7] makes the scale of the problem very clear. For laptops and similar computers, manufacturing, distribution and disposal account for 52% of their Global Warming Potential (i.e. the amount of CO₂-equivalent emissions caused). For mobile phones, this is 72%. The report calculates that the lifetime of these devices should be at least 25 years to limit their Global Warming Potential. —https://wimvanderbauwhede.codeberg.page/articles/frugal-comp...

[jrmg]

The carbon cost to produce or use a new phone isn’t relevant here.

The important question is whether repurposing an already-existing phone to act as a server (including physically adapting the phone and producing whatever extra hardware is required to do that) is less carbon-costly than producing and using a new designed-for-the-purpose server.