My experience:
- maximum size to read from (both USB and SATA) - I do not know, I tried 22 TB and it worked (GPT, NTFS)
- maximum size to write to - 17.6 TB as per my experience. If HDD is larger - writing to the disk is not possible, no data is saved properly and can be recovered by chkdisk on PC later only. So HT work/Kodi editing etc will be impossible. More: disk work will become VERY unstable - slightest mistake and data is gone. Had such experience, had to recover 18 TB of films :-(((
Point: all above is for VOLUME. Hence if HDD is partitioned to 2 or more volumes not more then 17.6 TB each - everything works fine (WD DC HC550, Seagate Exos, GPT/NTFS, 512 bite/sector, 4096 bite/cluster).
Do not know about Dune, but Zidoo 1000 Pro can read partitioned HDD without problem.