successful project
That is a very biased claim. It’s like saying that the PS5 is the most successful gaming platform because God Of War: Ragnarök and Ghost Of Tsushima players prefer it over Xbox and PC.
If you go to snapcraft.io, you can see snap being installed on many other distributions other than Ubuntu. It will not show you the exact numbers, but people willingly install it on their machines. I think that’s successful.
I don’t think “there exists an unknown number of non-Ubuntu machines with snap installed” is a valid metric when the general sentiment seems to be apathy. It’s popular for the same reason Internet Explorer was popular – it’s forcibly installed with the default OS.
If the numbers were favorable, Canonical would release them.
What is the “general sentiment” tho? Sure, on Lemmy and Reddit communities I usually see people hate Snaps, but that’s just a few thousands of people. Another metric of success could be developers maintaining their software as snaps. You will find that quite a lot of them do so.