@nicu thanks for asking! You could compare:
dpkg -l | grep -i ldap
ldd seaf-fuse seaf-server (directory i.e. /home/seafile/seafile-server-8.0.5/seafile/bin)
and check this also, but I think you already know about it:
and here the seafile “manual”:
https://manual.seafile.com/deploy/using_ldap/