You are not allowed to use Lightsail once you use more professional services on AWS atleast per ToS

Do you have a more detailed citation for that? At $DAYJOB we seem to be using Lightsail (for non-cache purposes) along with some "real AWS" resources without a problem,

AWS Service Terms[0]

51. Amazon Lightsail

51.3. You may not use Amazon Lightsail in a manner intended to avoid incurring data fees from other Services (e.g., proxying network traffic from Services to the public internet or other destinations or excessive data processing through load balancing or content delivery network (CDN) Services as described in the Documentation), and if you do, we may throttle or suspend your data services or suspend your account.

[0] https://aws.amazon.com/service-terms/

I think you’re expanding this clause past what it says.

The clause prohibits you from using Lightsail to cheat other services. So, per their example, you couldn’t set up a Lightsail instance as a reverse proxy between the internet and an ELB, to take advantage of Lightsail’s higher transfer quotas and “in-region” traffic from Lightsail to ELBs.

Hosting a site on Lightsail and hosting other things on other AWS services is fine.

I am not the OP. The terms indicate you cannot use it to proxy traffic to bypass bandwidth costs. The grandparent comment suggested using Lightsail to do this, and it is a violation of the TOS. The parent comment, however, stipulated that you are not allowed to use Lightsail at all, which is indeed wrong. I was just posting the relevant portion of the TOS which applies to the grandparent comment, and clarifies on the parent comment (which is inaccurate)

Thank you for the correction! Second time I made this claim but always forget it’s just about the traffic…

That's insane. But not a surprise, lightsail only exists so aws can say they offer similar pricing to Linode/DigitalOcean/Vultr/etc... as long as you don't ever plan to grow

Interesting. In this example where the parent comment discusses using a proxy from AWS to Linode/Hetzner to Cloudflare, then I'd go with someone in the Bandwidth Alliance, which would include Linode and Vultr.

Have either of those actually implemented Bandwidth Alliance? Last I looked(few months ago), the only outfit that had actually done anything on that was Backblaze. Vultr and Linode were nothing more than announcements with no actual cost savings for customers implemented.