I put changedetection.io to notify me on Telegram of changes on the registration page ;)

It was opened for 1 hour together with CHD

you can generate a new cookie with the value you want to identify that computer and use/capture that same value in the plausible custom event

In Plausible you can use custom events: https://plausible.io/docs/custom-props/introduction

I think this should be enough

Use https://home.tdarr.io/, it has what you are looking for and will do everything automatically! The first setup is never easy!