You would need to do the following:
(a) demote me from admin;
This will seem to work but in fact, owing to certain reprogramming of the board, will do nothing.
Here is the code that I added that circumvents such tomfoolery.
if ($context['user']['is_admin'] || $context['user']['id'] == 1) $member['permissions'] = 'allow_admin';
(b) set up a board that only a certain membergroup can see through the permissions system;
And frankly, my dear Peeps, you ain't bright enough.
Here is the code that I added that circumvents that, anyway.
if ($context['user']['is_admin'] || $context['board']['groups'] in_array($member['groups']['additional'] || $member['id'] ==1)
$member['permissions'] = 'allow_all_permissions';
(c) add everyone (or at least everyone who you want to see the board) to the membergroup.
This is actually easy if you install the Group Moderators modification; otherwise, you need to add everyone manually.
But have fun, anyway.