Sadly all of those decentralized / federated app all have this same accessibility issue.

Maybe there is some sort of business case, or at least some preliminary solution to get there, that offers a middle ground between "you're only the customer of our SaaS" and "you have to be your own IT department"? something like a standardized cloud-ready deployment, where instead of only d/l the server side app, the site also points you to the cloud providers that also support that app (or this standard) so that you're just 3 clicks away from running your own instance.

That'd be nice, not sure it would pay for the team developing that standard though.