Activity feeds are enabled for some out of box entities automatically in CRM for specific actions. Recently there was a query on CRM community how to be able to create posts when an Entity is updated.

Solution: Create an out of box workflow on entities you want to have auto post on updates.

Step 1: Taking example of lead entity, create a workflow on update of lead entity:

Note: It is not necessary to create synchronous workflow.

Step 2: All fields must be selected in Records field change (If you want specific, you can update specific):

Step 3:

Create Post in the processing step:

Step 4: Activate this, follow a lead record (Follow button via ribbon). Your changes will now start appearing in What’s new area as well as posts area on the record:

What’s new area below:

Posts on Record’s wall :

Hope it helps!