Doesn't SoGo use Activesync? This wouldn't need an app on your phone.
I tried the same setup as you a few years ago. It worked, but I didn't like SoGo for email so moved to Nextcloud/SnappyMail and DAVx/K9 on my phone. Have been using this fine since.
It does allow sync for each of your LDAP users, but it may require an app on your phone. I use the same setup and have had success with DAVx on android.