"Is there a way to give a specific group of team members access to every board?"
This is easy to do with a Taskfeed Board Sharing Rule. The Sharing Rule can be based on who owns the Board or a Criteria of the Board; e.g., Board Type. Or just for all boards. If these team members are not in a Public Group yet, you will need to create a Public Group that includes these users.
Defining Sharing Rules
To create a Public Group:
Go to Setup > Manage Users > Public Groups
Select “Users” under “Search for” to add individual users to a new Public Group.
Now Create the Sharing Rule that allows this Public Group access to every board (or any other criteria):
From Setup, type Sharing Settings in the Quick Find bar.
Scroll all the way down to Taskfeed Board Sharing Rules
Select whether you want to share based on Record Owner or based on Criteria.
To select the users you want to share the rule with, select the Public Group where those users belong to.
Examples of Board Sharing Rules:
Create a sharing rule using the default public group 'All Internal Users' to share with 'All Internal Users' then decide the Access Level.
Example 2: Share only some Boards with all Users Read-only
If we only want to share certain boards with all users then we first want to create a custom field on the Taskfeed Board to help determine which Boards to share. This could be a just a checkbox which the owner could check to make the Board Public.
When defining the sharing rule you will want to select rule type 'Based on criteria'. Then select the criteria as 'Public' equals 'True'. Then select to share with 'All Internal Users' then decide the Access Level.