1. Domain Alias Support at the Cloudron Level (since this would be helpful to all apps, not just WP Multisite)
2. Official Wordpress Multisite Top-level Domain Support on Cloudron (which would use domain aliases to accomplish this as that's the only feature needed for *full support of WP Multisite)

I'll be writing a custom Cloudron Wordpress plugin to automatically add top-level domains added to WP's multisite feature directly as a domain alias on the Cloudron app itself. I did this same thing for CPanel and it worked perfectly. Your API is even simpler than CPanel's so it should be even easier to write this for your platform.

I’m loving Cloudron more and more as I’m learning more about it. I think I want to use it for production one day but if this was what was holding me back, I just wonder if there is a plan to support this because WP Multisite’s built in feature is multiple domains (or sub domains, but I chose top level domains for my 3 sites within the multisite).

On Cloudron each app gets a unique single origin/domain which then is used to route through the reverse proxy to the app. This means that a single app cannot run on multiple domains. The alternate domains you can set are only redirects. Thus unfortunately a wordpress multisite setup with more than one domain will not work on Cloudron. Multisite setups only work if subpaths instead of subdomains are used.

It sounds like what you're actually saying is that even if subpaths are used it's not possible to have a multisite with more than one domain, right?

So:

blognetwork.coop/blog1/
blognetwork.coop/blog2/
Etc

Would work.

But these urls cannot be mapped to any other top level domains.

So, it's impossible to migrate my WordPress Multisite which has 7 sites all at different domains to Cloudron, even if subpath method is used, correct?

I thought as much, but good to know for sure.

I think it's probably worth adding at least the bit I've bolded above to the docs about WordPress apps somewhere.