Alpine LXC container - apk update fails

I have setup my raspberry pi 4, to have ubuntu 18.04. I see uname -m as ( aarch64).
I am able to create ubuntu lxc container and I can open interactive shell , can install jre in it.
But, with alpine container, I am not able to install jre in it, basically the apk update fails.
I tried changing mirrors, but did not work. Looks to me that with alpine there is some network issue/unable to access a URL such as a repository. Thanks for any help.