Lex and Connect

Yes, it is still true that Amazon Lex and Amazon Connect must be in the same AWS account for integration to work. This requirement has not changed.

While Amazon Lex and Amazon Connect can be in different AWS Regions, they must be within the same AWS account. This is a limitation of the integration between these two services.

It's worth noting that while cross-account access isn't supported, you do have some flexibility in terms of region. You can have your Amazon Lex bot in a different AWS Region from your Amazon Connect instance. However, it's considered a best practice to have your Amazon Lex bot in the same Region as the Connect instance for optimal performance. If you use an Amazon Lex bot from another Region, it might result in suboptimal performance.

Unfortunately, I cannot provide a direct link to the documentation, but this information is still current and can be found in AWS's official troubleshooting guides for Amazon Lex integration with Amazon Connect.
Sources
Troubleshoot Amazon Lex integration failures | AWS re:Post

Yes, Amazon Lex and Amazon Connect must still be in the same AWS account for integration to work properly. While these services can be in different AWS Regions, they must remain within the same AWS account due to integration limitations. For optimal performance, it's recommended to have your Amazon Lex bot in the same Region as the Connect instance.