When enabling wsrep_gtid_mode as 'ON,' Galera should take into account the wsrep_gtid_domain_id value for GTID across all nodes within the same Galera cluster.
However, this consideration does not occur if the wsrep_gtid_domain_id is defined as anything other than the default value of 0 except bootstrap node.

As per documents https://galeracluster.com/library/documentation/mariadb-options.html#mariadb-options

When wsrep_gtid_mode is set to ON, wsrep_gtid_domain_id is used in place of gtid_domain_id for all Galera Cluster write sets.

Impact of the same :

Replicating from one Galera cluster to another Galera cluster will result in a break in replication.
This is because mariabackup may not maintain consistency with the GTID values captured within xtrabackup_binlog_info.

The failure of bi-directional replication occurred when attempting to connect two Galera clusters due to the requirement for a distinct wsrep_gtid_domain_id value.
As a result, adding a Slave node to the Galera cluster replication becomes the only viable solution.

Test Cases(Failed) :-

10.5.21

galera-4-26.4.14-1.el7.centos.x86_64

wsrep_patch_version wsrep_26.22

wsrep_provider_version    26.4.14

10.5.22

galera-4-26.4.14-1.el7.centos.x86_64

wsrep_patch_version wsrep_26.22

wsrep_provider_version    26.4.14

10.6.15 

galera-4-26.4.14-1.el7.centos.x86_64

wsrep_patch_version wsrep_26.22

wsrep_provider_version    26.4.14

GTID related Parameter configured on nodes

Node-01

server_id=901

gtid_domain_id=204

wsrep_gtid_domain_id=9898

wsrep_gtid_mode=ON

gtid_strict_mode=OFF

Node-02

server_id=901

gtid_domain_id=205

wsrep_gtid_domain_id=9898

wsrep_gtid_mode=ON

gtid_strict_mode=OFF

If the user defines a value other than 0 (default) for wsrep_gtid_domain_id, Node-02 will always take into account wsrep_gtid_domain_id=0.

Test Case(Success) :-

10.5.18  and lower version having Galera version 4 (26.4.13)

galera-4-26.4.13-1.el7.centos.x86_64

wsrep_patch_version wsrep_26.22

wsrep_provider_version    26.4.13

MariaDB Server bundled with wsrep_provider_version 26.4.13 can be used without any issues