Downgraded to Nextcloud 26 with exact same LDAP setup, this works slightly better.
Required less changes to Advanced (only changed the displayname lookup to ‘name’) and Expert (only enabled UUID override for users: ‘uid’)
LDAP config shows the correct amount of users and groups. LDAP user can log on ánd the ‘users’ interface works.
Currently, I only see the users though. In the LDAP config test, 6 groups are found, but they do not show up in the interface, or in apps like ‘group folders’.
Mentioned here