If you are using Apple Business Essentials as your MDM, then you can only use .pkgs. See here for details:
Intro to deploying packages in Apple Business Essentials - Apple Support
However, Apple does not provide a cloud distribution point so you need to host the files yourself. See the article for suggestions on what to use. Do NOT open up file sharing to the Internet.
Apple Business Manager (not with Essentials) is not an MDM. ABM is a chain of custody and identity trust tool only. For example, you can license App Store apps in ABM but you cannot deliver them without an MDM. Likewise, you need an MDM to deliver 3rd party software. This would be Apple Business Essentials or another MDM.
If you have applications that are distributed via DMG or .app stub installers, you will need to build your own pkg installers after installing the software on a reference machine. You can look into pkgbuild (man pkgbuild in Terminal) or try to pick up a copy of Composer from Jamf. Manually creating package installers is an art and requires a bit of practice. Also, you may need to sign and notarize the packages you create if you are using Essentials since I do not believe Apple has the ability to run scripts on the target device. Gatekeeper will likely reject your custom pkgs as they will identified as being from an unknown developer.
Hope this helps.
