Postgres 12 won't start in HA cluster after "recovery.conf" is not supported error

Issue

After an upgrade of the Postgres application, instances fail to start with below error:

Jan 28 13:22:05 localhost postgres[22617]: [8-1] postgres-log ibm-sbx     61f4344d.5859  0 2022-01-28 13:22:05.438 EST [22617] FATAL:  using recovery command file "recovery.conf" is not supported <--- Fatal error

After this error the cluster node repeatedly reports "PostgreSQL" as down, until the start operation ultimately times out:

Jan 28 13:22:05 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:06 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:07 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:08 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:09 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:10 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:11 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:12 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:13 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:14 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
----------------------------------------------->8-------------------------------------------------
Jan 28 13:22:56 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:57 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:58 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:22:59 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:23:00 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:23:01 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:23:02 localhost pgsql(postgresRA)[22419]: INFO: PostgreSQL is down
Jan 28 13:23:03 localhost lrmd[3793]: warning: postgresRA_start_0 process (PID 22419) timed out <--- timed out during startup
Jan 28 13:23:03 localhost lrmd[3793]: warning: postgresRA_start_0:22419 - timed out after 60000ms
Jan 28 13:23:03 localhost crmd[3796]:   error: Result of start operation for postgresRA on localhost: Timed Out
Jan 28 13:23:03 localhost crmd[3796]: warning: Action 1 (postgresRA_start_0) on localhost failed (target: 0 vs. rc: 1): Error <--- error code 1 returned