Newbie to containers, I have 50+ domains I want to monitze by getting them facing the public by deploying in a single container.
A local single container that contains nginx reverse proxy, react and some backend to serve 50+ sites (probably like 5 visitors a day ;). Then upload that container on some VSP. Is that a reasonable doable simple thing?
Yes. Totally no problem.
Nginx as reverse proxy is good.
Rendering different thongs based on the domain is not an issue. Either have multiple "server" blocks in your nginx config which point to different React apps, or have a single React app that just renders different things based on the hostname.