External db recommendation rewording and DMS exclusion

doc/administration/geo/setup/external_database.md

@@ -17,9 +17,10 @@ to [avoid version mismatches](../index.md#requirements-for-running-geo)
 in case a Geo site has to be rebuilt.
 
 NOTE:
-We strongly recommend running instances installed using the Linux package as they are actively
-developed and tested. We aim to be compatible with most external
-(not managed by Omnibus) databases but we do not guarantee compatibility.
+If you’re using GitLab Geo, we strongly recommend running instances installed by using the Linux package or using
+[validated cloud-managed instances](../../reference_architectures/index.md#recommended-cloud-providers-and-services),
+as we actively develop and test based on those.
+We cannot guarantee compatibility with other external databases. 
 
 ## **Primary** site
 
@@ -81,6 +82,11 @@ cloud providers:
 
 When your read-only replica is set up, you can skip to [configure your secondary site](#configure-secondary-site-to-use-the-external-read-replica)
 
+WARNING:
+The use of logical replication methods such as [AWS Database Migration Service](https://aws.amazon.com/dms/) 
+or [Google Cloud Database Migration Service](https://cloud.google.com/database-migration) to, for instance, 
+replicate from an on-premise primary database to an RDS secondary are not supported.  
+
 #### Manually configure the primary database for replication
 
 The [`geo_primary_role`](https://docs.gitlab.com/omnibus/roles/#gitlab-geo-roles)

doc/install/requirements.md

@@ -116,10 +116,12 @@ Support for [PostgreSQL 9.6 and 10 was removed in GitLab 13.0](https://about.git
 
 #### Additional requirements for GitLab Geo
 
-If you're using [GitLab Geo](../administration/geo/index.md), we strongly
-recommend running instances installed by using the Linux package, as we actively develop and
-test based on those. We try to be compatible with most external (not managed by a Linux package installation) databases
-(for example, [AWS Relational Database Service (RDS)](https://aws.amazon.com/rds/)), but we can't guarantee compatibility.
+If you're using [GitLab Geo](../administration/geo/index.md), we strongly recommend running instances installed by using the Linux package or using
+[validated cloud-managed instances](../administration/reference_architectures/index.md#recommended-cloud-providers-and-services),
+as we actively develop and test based on those.
+We cannot guarantee compatibility with other external databases.
+
+It is recommended to review the [full requirements for running Geo](../administration/geo/index.md#requirements-for-running-geo).
 
 #### Operating system locale compatibility and silent index corruption