Thanks for the input on this question.
As mentioned by @RGJ , our enterprise infra uses external services for things like cache, database etc hence the Elasticache and RDS. It means we can have full backup and redundancy for these services and also help with security controls. This is an official/supported installation from a Discourse point of view - its just using a different set of templates - we use discourse_docker/samples/web_only.yml at main · discourse/discourse_docker · GitHub (maybe using the word standard was a bit misleading, apologies).
So, sounds like we should first update our bucket names for the existing install and then perform the move to the new server. Updating the existing install to the latest version is a no go - we experienced issues with the Bitnami upgrade previously hence the move to the official installation method.
Can I ask though, what issues are likely to happen if we perform the restore with the existing buckets and then update the app.yml to reference the new buckets - don’t all of the DISCOURSE_ env vars take precedence over any config in the database (if applicable)? Or is there something else that could cause a problem?