Hi Gary. Right now, I can upload a maximum file size of 50MB, limited by me on my Moodle.
In php.ini, I have set upload_max_filesize to 128M, and post_max_size to 128M.
Then, in Moodle, go to Site administration / ▶ Plugins / ▶ Activity modules / ▶ Assignment / ▶ Submission plugins / ▶ File submissions. I set my limit to 50MB, but I do see that I can go as high as 128MB.
Then, in the course, (in a forum or in an assignment) you can set the upper limit for file attachments. In one of my courses, I set this to 50MB. But in most of my courses, I set the course limit to something much smaller than 50MB, and the activity file size limit to whatever seems appropriate, such as 5MB.