It looks like https://jdk.java.net/17/ says alpine build is not available, but the alpine repo has a package. https://pkgs.alpinelinux.org/package/edge/community/x86_64/openjdk17-jre
Any idea why this happens? Does this means alpine uses an early access build? not GA? How can we confirm this?
The first page you linked explains why the Alpine build has been removed:
"The Alpine Linux build previously available on this page was removed as of the first JDK 17 release candidate. It is not production-ready because it has not been tested thoroughly enough to be considered a GA build. Please use the early-access JDK 18 Alpine Linux build in its place."
Does this means alpine uses an early access build?
I doubt it.
Not GA?
Well, the GA builds were deemed to be not "GA quality" ... due to lack of testing.
But if you compare the build name (e.g. 17.0.2_p8-r1) with the tags in the OpenJDK repo (here), it looks like the Alpine builds are tracking the 17u updates. Indeed, it looks they are what the GA builds would have been ... if the team had been willing to apply the "GA" label to them.
This is moot if you follow the recommendation of the OpenJDK site and use the early-access JDK 18 Alpine Linux build instead. Presumably they recommend this because they think it is better quality ... despite being early access!
How can we confirm this?
You could contact the person responsible for creating the Alpine builds. Or you could look at the evidence yourself.