I'm beginning to form my own answers on this, but the full understanding will take a lot of research and log review, so please edit, post other answers, and/or comments here!
In an older guide for OSX Server, I've read these comments, but surely rather than being required to allow guest access to those shares, a local account on the Server can mount them, or maybe that information is from before the authenticated-mounting made its way to OSX:
Be sure to enable guest access both for the share point and for the
protocol under which it is shared.
Note: Automounted share points are available to clients only when their computers start up.
One element of this problem can be explained by reading over the Open LDAP documentation, which Apple's Open Directory is based on. I have seen from time to time, at least once of the messages they describe, in the Open Directory logs.
Deep within OSX there may be inconsistencies of BerkleyDB versions, which for the simple-end-user in a perfect world could be resolved between the ideal combination of versions of OSX on the client, OSX (on the server), and Server.app or other changeable componts, also on the server.
from the link:
C.2.9. ldap_sasl_interactive_bind_s: Can't contact LDAP server (-1)
Using SASL, when a client contacts LDAP server, the slapd service dies
immediately and client gets an error :
SASL/GSSAPI authentication started ldap_sasl_interactive_bind_s: Can't contact LDAP server (-1) Then check the slapd service, it stopped.
This may come from incompatible of using different versions of
BerkeleyDB for installing of SASL and installing of OpenLDAP. The
problem arises in case of using multiple version of BerkeleyDB.
Solution: - Check which version of BerkeleyDB when install Cyrus SASL.
Reinstall OpenLDAP with the version of BerkeleyDB above.
http://www.openldap.org/doc/admin24/appendix-common-errors.html
Apple has introduced a new file system APFS in High Sierra. The easy fix is to verify your backup and then erase the volume and run the installer against a blank / erased main storage drive.
Because the APFS requires support from a new version firmware, your mac's firmware will have to be updated to the latest version during the installation of High Sierra.
After the first restart, the installer prepares the latest version firmware which suitable for your mac model onto EFI system partition of your main disk with bless command. Then restart automatically and trigger the firmware upgrade process. (marked as point A)
After the upgrade process (regardless success or fail), the installer continues. It double checks the version of firmware to make sure it was updated successfully in previous process (namely point A). As a result, the installer find out that your firmware is NOT a latest version still. Hence, it reports "An error occurred while verifying firmware". Yes, it is what you saw on the screen.
The root cause of the failure at point A, in your case, is no internal drive in main bay. The firmware upgrade process only recognize the ESP (EFI System Partition) of primary internal drive. That means the upgrade process was interrupted.
So, you might have to get the primary SATA port work and connect your disk to it. It's said that, most of time, it is the hard drive cable which is out of order, instead of the chipset. If that is the case, it probably can be fixed within $20 to get a replacement. And that was my case. :)
Best Answer
macOS Server is keeping LDAP with no published plans for it to be removed. See: