alpine-mirrors apk is missing in 3.13.x
No alpine-mirrors apk in 3.13.x distribution, setup-apkrepos has nothing to choose from. Normal install from scratch is not possible.
Manual correction is possible, but requires a prior version of Alpine handy.
An example:
# setup-apkrepos
wget: error getting response
wget: error getting response
r) Add random from the above list
f) Detect and add fastest mirror from above list
e) Edit /etc/apk/repositories with text editor
Enter mirror number (1-0) or URL to add (or r/f/e/done) [1] f
Finding fastest mirror...
Warning! No mirror found