This image should be used only when you are testing changes made to the docker container code itself, but the Pi-hole components inside this image may not be the most recent. Usually this image is not updated very frequently.
If you want to use the development branch of all Pi-hole components you should use pihole/pihole:nightly image.
I don't want to sound negative, but neither one of your replies did answer the question. IPv6 is obviously enabled, since the Docker instance receives multiple IPv6 address prefixes, just not a default route, and after manually adding a default route, IPv6 works without problems. And unless there is an IPv6-specific difference between latest/nightly/development, I'll stick with development, since this is absolutely a testing environment.
As I said, pihole/pihole:development is not the correct image to test Pi-hole Core development + Web interface development + FTL development...
At the moment, while we are actively making changes in all repos (including Docker repo) you won't notice the difference, but development image is updated only when docker-pi-hole repo is updated.
If we update the development branches of all other 3 repos, but not docker repo, this image won't be updated.
The nightly image will always contain the most recent development branches.
About your Mikrotik issue:
Sorry. I can't help. I don't use Mikrotik.
I take it back, deleting all stores and mounts and switching to nightly did allow the pihole container to receive a default IPv6 route after all. Not sure what to make of that. Thank you for the pointer though. If "development" branch is a problem, it shouldn't be advertised anyway.
It is not a problem to use, but it is used to develop docker-pi-hole repository code.
Users are welcome to test that code (that's why we don't hide it), but usually users want an image with the most recent development branches from the other 3 repos. I think that's your case (like most users).
In this case, the correct branch is pihole/pihole: nightly.
