Without using code for 21K users, I can get it to 42 quick actions – or the same action 42 times !
NOW be careful – make sure you know who you want to be different – eg administrators, as if you bulk change and then log out without changing back, then you may lose admin access – and then you’ll need to use phpmyadmin using nasty sql stuff to correct this.
So start by making a list of users with admin, or other wordpress roles you’ll want to be different – write these names onto a post it note and stick this to your screen so you won’t forget !!!!
Then go into
Dashboard>users>all users
At the top right of the page you see ‘screen options’ click this and typically you’ll see a part that says
20 users apply
Change this to 999 users and click the apply box.
This will then display 999 users at a time, so you can bulk change 999 in one go.
Then next to the ‘username’ heading you’ll see a tick box which is the ‘select all’ option, click this and it will select all 999 of page 1 users
Above this you’ll see a ‘bulk actions’ and then the bits we want to the right of that – the ability to change the wordpress and forum roles.
So having ticked to select all the 999 users displayed on page 1, click the ‘change role to’ and select the subscriber role, and then the change box, and hey presto all 999 are now subscribers.
Tick the ‘select all’ again, and select the bbpress participant role, and change that.
so now all page 1 users are correctly set.
Now select page 2 on the right just below the bulk change forum role and repeat !
So for each page (21 or 22 of them) you do
Select page
click ‘the select all’ box,
click forum to ‘subscriber’ and click change
click ‘the select all’ box,
click role to ‘particpant’ and click change
select next page
THEN!!!!!!!!!!!!!!!!!!!!!!!!!! CHANGE THE ADMINS BACK BEFORE LOGGING OUT !!!!!!!!!!!!!!!!!!
Probably taken me longer to type these instructions than for you to execute them !
Mod Note: I edited your post Robin 😉 Cheers, Stephen