Moving to AWS Transit Gateway from VPC Peering

You can use [Serverless Transit Network Orchestrator] (https://docs.aws.amazon.com/solutions/latest/serverless-transit-network-orchestrator/deployment.html) to deploy hub and spoke model using Transit Gateway. There's an option to add Route to TGW, this will add route to VPC route table associated with the subnet but it will not overwrite existing route. So if you have route going to VPC peering that will not get overwritten.

You can deploy this and have default route or wider CIDR range (less specific route) under Default Route to TGW Example if you have 10.1.0.0/24 -- VPC-peer1 and 10.2.0.0/24 -- VPC-peer1in VPC route table, you can have 10.0.0.0/8 under Default Route to TGW. Once the solution is deployed and you have correct route in place, you'll have to manually delete VPC peering route.