How to download photos from iCloud (iPhone 4)

I have an old iPhone 4 that I am about to give up. It contains a few hundred photos and I briefly looked for a way to access it directly from my Xubuntu laptop. (I no longer have Windows or Mac machines.) However, I decided not to follow this route and open an iCloud account, save the photos and download them from iCloud via my browser. No problem, right?

Except that Is seems to be a problem. In iCloud.com, it is indicated that my iDevice should run on iOS 8.x (I do not remember the exact version), and that my phone runs under 7.x, so I guess the photos do not come out. do not display. I therefore thought that I could get them from iCloud Drive and download them en masse without the benefits of the pretty vignettes, but there is nothing either, despite the fact about 800 MB was downloaded from my phone.

I am looking for suggestions on how to get these pictures on this old iPhone or on iCloud if they are somewhere. Thank you.