Subliminal I have done three GrapheneOS installs so far.
The first was in 2019 and was a bit of an adventure, but part of that was that I built from source. I don't think there was a web installer, so after some false starts I got the command-line install to work.
The second was trying to use the web installer in Vanadium on a Pixel3a running GrapheneOS to install onto a Pixel 6a. That didn't work -- some step kept failing after a long time and eventually I gave up on it. I then tried with the web installer on Ubuntu, but not with a recommended browser, and that failed too.
So I fell back to the command line again, and that worked.
Whatever method you try, it is important to follow the directions very carefully. Anything specific in the directions (e.g., use Browser X or else Browser Y) is there because substituting something else has failed for a bunch of people (if the directions say "Chrome", that does not extend to other browsers that contain some amount of code from Chrome; it means exactly Chrome). Also, if some step doesn't work, stop and ask for help, because the steps are not skippable, and doing things out of order could potentially brick your device.
I guess the short answer is that if a reasonably competent Linux user follows the directions carefully and exactly then it is very likely to work - for either the web installer or the command-line procedure. If the web installer works, it is much harder to make a mistake with it.
Good luck! Follow the directions carefully and exactly!