Lightsail instances connecting to general aws free-tier load balancer

I have a AWS free account with lightsail free trial.

I deployed 2 instances of Odoo with Nginx connecting to 1 database. All these were set up in AWS lightsail. Then I wanted to connect to load balancer and I found load balancer in lightsail aren't included in lightsail free trial.

Then I tried to find ways to connect my system to AWS elastic load balancing as it is free with 12-month free period. And then I found the below post saying that it is hard to connect them:

https://stackoverflow.com/questions/61283783/how-do-i-use-a-ec2-load-balancer-with-aws-lightsail-instance

So my question is: I have Odoo with Nginx connecting to 1 database in aws lightsail. Is it possible to connect to elastic load balancing in general aws free tier? If yes, some brief instructions would be appreciated.

For testing purpose, I tried to do connection between lightsail and general aws. But it seems that they are in 2 different groups and I couldn't do that. I didn't know whether I set it up wrongly or it is indeed impossible.

Thank you.