grub-install defaults to partition on whole disk raid array rather than underlying disk or whole raid array

According to your logs the subsequent attempts reported failure as well. This is because of a known bug in ubiquity that causes all subsequent attempts to fail after the first one has. Please try again and select the correct drive the first time, which would need to be your actual boot disk, i.e. /dev/sda.

Thanks @psusi for your comment. The problem is that when selecting the default settings as I described there is no option of sellecting /dev/sda.
What should have happend when a user selects default (Erase everithing and install Ubuntu) grub-install should detect RAID aray and install it aproprietlly. Instead what happens is, as I described grub fails with grub-install /dev/md127p2 failed and propmts you to select other partition where ther is NO /dev/sda as option only : /dev/md127, /dev/md127p1, /dev/md127p2, /dev/md127p3.

Inspecting more on the matter (mostly googling and readyn tuts) I see there are some issues with Grub and RAID. With a quick search here there is a Bug #752694 seems related with mine. Should I mark mine as duplicate of Bug #752694 ?

No, this is unrelated to that old report that was invalid anyhow. I was able to reproduce this with mdadm --create -e 1.0 -n 2 -l 1 /dev/md0 /dev/sda /dev/sdb, then going through the install, it tried to install to a partition on the array. Interestingly, when I omit the -e 1.0, it tries to install to /dev/sda, as it should, but this fails since the default 1.2 metadata format does not leave room for grub.

I have this problem too, except that I am trying to install on an actual hardware RAID.

Please don't randomly mess with the bug status.

Firstly, people if you don't intend to commit yourself on fixing it don't mess with the status. If you change the status, please add a link to the commit/patch that fixed the issue.

Secondly.... it's been 4 years !!! What is going on with this bug ? Are you just waiting to the EOL of Ubuntu 14.04 so it will be an obsolete bug report ?

got issues while installing 19.04 ubuntu .unble to install grub2 .

Closing this bug 'wontfix'. Full-disk software RAID is incompatible with UEFI which almost all amd64 systems include nowadays. Ubuntu 14.04 LTS, while still supported, is not undergoing any further development work, only security fixes; and no further install media will be issued. I do not know if this bug is fixed in later releases of Ubuntu, but ubiquity which embeds grub-installer is also not undergoing further active development, we are in the process of replacing it with a frontend to subiquity. But subiquity will also not want you to use full-disk RAID, again because it's incompatible with UEFI.