SMB2 cannot be navigated as the Kodi thread you linked to stated. You need to type in the access information. If guest access is working the advancedsettings.xml would work. In your last logs it still is not.

For the RPi you need to make sure that you have the right version of Librelec to access SMB2 https://wiki.libreelec.tv/accessing_libreelec

Martin