Adding users to Channels/Groups

I really want to push my users to Zoom chat & channels over teams but I'm struggling with adding users.   We have SAML mapping done to add our users to a group based on AD location, but ZOOM limits SAML mapping to only the first claim so everything else is ignored.  

I've finally conceded and created 50+ channels and manually added users to those channels, but I have a few channels that need every user in the company added to them.   I really don't see an easy way to do this.   If I create a group and try to add members, I can only add them one at a time and a limit of 10 in a batch.  Same goes for channels.    

Does anyone have any tricks on managing members of groups or channels since the AD SAML mapping is limited?   

Thanks!