transfer Elastic IP addresses from one AWS account to another?

Yes, it is possible to move an elastic IP address across accounts. All you have to do is Open a support cases from both the source and destination accounts to authorize and acknowledge the transfer

---request content---
Elastic IP: 
source account id: 
target account id:  
Use case description:
---------------------

Once the transfer is completed internally by the Support:

Source account A needs to release the EIP.

Target Account B allocates the EIP using the following aws cli

$ aws ec2 allocate-address --domain vpc --address [EIP]

https://docs.aws.amazon.com/cli/latest/reference/ec2/allocate-address.html

Please also note An Elastic IP address is for use in a specific Region only, and cannot be moved to a different Region.

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html#eip-basics

Hope this helps

Elastic IP address transfer can now be done from the AWS console. It is no longer necessary to open support cases to transfer an Elastic IP address. If an Elastic IP address is locked to the account then a support case will be required to have that Elastic IP address unlocked first before you can transfer the Elastic IP address. Please refer to the following article, https://repost.aws/en/knowledge-center/vpc-transfer-elastic-ip-accounts