is there any OOTB group which provides Read only access to its users?
There is no OOTB group present for this purpose. I would suggest to create group and allocate permissions as per your needs because it makes no sense that you need full read access, you must be needing access to certain hierarchy only, so makes use of custom group.
I doubt there is any such group OOTB.
But, it's really easy to create one such group.
You just have to create a group and give complete Read Access in /useradmin console. Ex: http://localhost:6440/useradmin
Steps to follow:
1) Go to http://<host>:<port>/useradmin
2) Create a new group by clicking Edit -> Create -> Create Group. Give any group id and group name.
3) Search for that newly created group. Go to Permissions tab of that group. Select Read for all the nodes, or for the root node, and click on Save.
4) Reload the page and/or lookup for that group. Double-click it. Go to permissions tab. If there's any Read access missed, check Read checkbox for those remaining parent nodes(such as /conf, /etc, /var, etc.) and click on save.
5) Verify once again by performing Step 3. You have created a group with Read-only access to all the nodes.
6) Now, you can add your users/groups under the Members tab of that newly created group.
You can also limit the read permissions, or give any other permissions on whichever nodes you want to, to meet your criteria/usercase.
I hope it helps !! 🙂