Kuma can actually do quite a lot, as long as for example your application provides an endpoint to connect to, Kuma can query it and check for specific content in the replies. It is much more than just a "is it up or down" tool.

If you are writing your own playwright tests do you have the skills to wrap these up in a web api? If so you can then use uptime-kuma to call your playwright tests and return 200 if it's ok or something else if not, Kuma will show the status code history in the dashboard so you could use specific codes for specific reasons, just try and keep them close to official. Or you could setup NodeRed to log more detailed responses to a database but you would then need to do more work to make a pretty way of displaying that, Grafana maybe?