Was testing this a little more, and there are further problems.
After installing the nodesource repo, it seemed to be ok, but at 1am the next evening, which I assume is when the update check is run on the slave, I began getting this error on every hotsync run.
I rolled back to clean install, installed the 3 repos, and the same thing happened again the next night at 1am.
PHP Fatal error: Uncaught Doctrine\DBAL\DBALException: Failed to connect to the database: An exception occured in driver: SQLSTATE[HY000] [2002] No such file or directory in /usr/share/nextcloud/lib/private/DB/Connection.php:64
Stack trace:
#0 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(429): OC\DB\Connection->connect()
#1 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(389): Doctrine\DBAL\Connection->getDatabasePlatformVersion()
#2 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(328): Doctrine\DBAL\Connection->detectDatabasePlatform()
#3 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(623): Doctrine\DBAL\Connection->getDatabasePlatform()
#4 /usr/share/nextcloud/lib/private/DB/Connection.php(151): Doctrine\DBAL\Connection->setTransactionIsolation(2)
#5 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/DriverManager.php(172): OC\DB\Connection->__construct(Array, Object(Doctrine\DBAL\Driver\PDOMySq in /usr/share/nextcloud/lib/private/DB/Connection.php on line 64
PHP Fatal error: Uncaught Doctrine\DBAL\DBALException: Failed to connect to the database: An exception occured in driver: SQLSTATE[HY000] [2002] No such file or directory in /usr/share/nextcloud/lib/private/DB/Connection.php:64
Stack trace:
#0 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(429): OC\DB\Connection->connect()
#1 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(389): Doctrine\DBAL\Connection->getDatabasePlatformVersion()
#2 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(328): Doctrine\DBAL\Connection->detectDatabasePlatform()
#3 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(623): Doctrine\DBAL\Connection->getDatabasePlatform()
#4 /usr/share/nextcloud/lib/private/DB/Connection.php(151): Doctrine\DBAL\Connection->setTransactionIsolation(2)
#5 /usr/share/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/DriverManager.php(172): OC\DB\Connection->__construct(Array, Object(Doctrine\DBAL\Driver\PDOMySq in /usr/share/nextcloud/lib/private/DB/Connection.php on line 64