It might be very difficult to discuss architecture and design questions, as they usually are heavy dependent on the context, scope, functional and non functional requirements, cost, available skills and knowledge and so on...
Personally I would prefer to stay with entirely server-less approach if possible.
For example, use a Cloud Scheduler (server less cron jobs), which sends messages to a Pub/Sub topic, on the other side of which there is a Cloud Function (or something else), which is triggered by the message.
Should it be a Cloud Function, or something else, what and how should it do - depends on you case.
I have a simple python script that I would like to run thousands of it's instances on GCP (at the same time). This script is triggered by the $Universe scheduler, something like "python main.py --date '2022_01'".
What architecture and technology I have to use to achieve this.
PS: I cannot drop $Universe but I'm not against suggestions to use another technologies.
My solution:

I already have a $Universe server running all the time.
Create Pub/Sub topic
Create permanent Compute Engine that listen to Pub/Sub all the time
$Universe send thousand of events to Pub/Sub
Compute engine trigger the creation of a Python Docker Image on another Compute Engine
Scale the creation of the Docker images (I don't know how to do it)

Is it a good architecture?
How to scale this kind of process?
Thank you :)
Run & scale simple python scripts on Google Cloud Platform