I would argue it is possible to run a business and be sustainable on open source, it's just harder and is not so compatible with the growth that many want.
I don't have an issue with this kind of license being used where open source does not suit, but I don't think we should change/widen the definition of "open source" to suit the sustainability needs of those that open source isn't compatible with, at the impact of the freedoms and open rights it provides.
The problem is that if you're not already differentiably the best at hosting your service right when you launch, someone else that's better at hosting can just do it and take all your business.
And hosting while keeping your prices down is not just a whole different skill set, anyone that's already a big will have pricing deals with AWS so they will beat you even if you host in the exact same way.
It's probably less differentiable in the case of something like Gumroad which is less likely to have big scaling problems, but for things like a distributed database, you run a serious risk of someone who is paying AWS half of what you are per compute hour just deploy the Helm chart and undercut you completely.
I've been sustaining myself for a couple of years now on my open source project (BookStack). Still going in a positive direction.
Other than that, some that come to mind: Proxmox, Opnsense, SnipeIT, GitLab, Canonical, Codeweavers/wine, Plausible, Home-assistant/open-home-foundation/NabuCasa, FreeBSD Foundation, Laravel, Blender, Godot.
Within there is a whole mix of business plans, some offer hardware, some are open core, some offer related paid services, some offer hosting, some offer support etc...
I don't have an issue with this kind of license being used where open source does not suit, but I don't think we should change/widen the definition of "open source" to suit the sustainability needs of those that open source isn't compatible with, at the impact of the freedoms and open rights it provides.