VPC -- Deletion of default subnets

Hello.

I think the solution is to create a new custom VPC and subnet or recreate the default VPC.
You can create a default VPC and subnet by following the steps in the document below.
https://docs.aws.amazon.com/vpc/latest/userguide/default-vpc.html#create-default-vpc
https://repost.aws/knowledge-center/recreate-default-vpc

Unlike services like lambda, EC2 resides in your VPC. Therefore VPC is needed to configure an EC2.

Follow this post for more information: https://repost.aws/knowledge-center/deleted-default-vpc