Yes, desktop in Chrome’s incognito mode. For this kind of test, a lot of elements matter and we don’t really master what and how… Because of this, I think it just has a relative sense instead of an absolute one ; I mean that it could be interesting to compare different results from our own context (each), but it’s impossible to compare different results from different sources – just because our contexts are different in a lot of points (location, computer, OS, browser, running pieces of software around, ISP, IPP, etc.).
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EDIT: Just to confirm the impact of context (including the browser’s one), here are some more lighthouse tests against one of your websites (always in incognito mode with last version of each browser).
In Opera for desktop:
In Opera for mobile:
In Firefox (using the Google Lighthouse extension) for desktop (we obtain the best result here ; even with my own websites that appear far from all-green with Chrome (see my first post above in this thread), it’s all green with this Firefox test):
In Firefox (using the Google Lighthouse extension) for mobile:
As you can see, it’s very context-dependent… We can only compare different results from the same location with the same browser into the exact same context!