Mariadb galera cluster master node started and reporting 2 nodes but second node service says activating mariadb I managed to start the master node mariadb galera cluster, then I started the second node and I check on the first master node;
$ sudo mysql -u root -p -e &quot;SHOW STATUS LIKE 'wsrep_cluster_size'&quot;
Enter password: 
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| wsrep_cluster_size | 2     |
+--------------------+-------+

but when I checked the second node it says:
 Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
   Active: activating (start) since Sat 2020-11-28 19:08:24 GMT; 11min ago
     Docs: man:mysqld(8)
           https://mariadb.com/kb/en/library/systemd/
  Process: 7659 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUC
  Process: 7660 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SU
  Process: 7662 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] &amp;&amp; VAR= ||   VAR=`cd /usr/bin/..; /usr/bi
 Main PID: 7829 (mysqld)
   Status: &quot;WSREP state transfer ongoing, current seqno: -1 waited 690.000000 secs&quot;
    Tasks: 12 (limit: 881)
   CGroup: /system.slice/mariadb.service
           ├─ 7829 /usr/sbin/mysqld --wsrep_start_position=00000000-0000-0000-0000-000000000000:-1
           ├─ 7837 sh -c wsrep_sst_rsync --role 'joiner' --address '192.168.5.132' --datadir '/var/lib/mysql/' --pa
           ├─ 7838 /bin/bash -ue /usr//bin/wsrep_sst_rsync --role joiner --address 192.168.5.132 --datadir /var/lib
           ├─ 7890 rsync --daemon --no-detach --port 4444 --config /var/lib/mysql//rsync_sst.conf --address 192.168
           └─10407 sleep 1

Nov 28 19:08:24 raspberrypi systemd[1]: Starting MariaDB 10.3.25 database server...
Nov 28 19:08:27 raspberrypi sh[7662]: WSREP: Recovered position 00000000-0000-0000-0000-000000000000:-1
Nov 28 19:08:28 raspberrypi mysqld[7829]: 2020-11-28 19:08:28 0 [Note] /usr/sbin/mysqld (mysqld 10.3.25-MariaDB-0+d
Nov 28 19:08:28 raspberrypi mysqld[7829]: 2020-11-28 19:08:28 0 [Warning] Could not increase number of max_open_fil
Nov 28 19:08:31 raspberrypi rsyncd[7890]: rsyncd version 3.1.3 starting, listening on port 4444

what does it mean ?
port 4444 is open on both the nodes.
I had the same issue with 2 nodes configured. mariadb-10-1-galera-cluster-error.
When using Galera Cluster, it’s recommended that the cluster have at least three nodes. In a two-node cluster, when there is a conflicting pair of transactions, it could lead to a split-brain situation. Also, when one node fails, the remaining node will become non-operational. (Two-Node Clusters)