You also can download directly into the device, and reboot to recovery by the advanced restart menu (enabled in settings → system → gesture) and simply “apply the update” without cable and computer…
Try to wipe cache…(from the recovery) it cost nothing…
Tab s6 lite is deffinitively THE WORST OF SAMSUNG SUPPORTED device to manage !
I had no problem to reboot by pressing all keys and to access recovery and download mode but reflashing the recovery/system and cleaning cache did not help so I now ended up doing a factory reset and have a fresh OS now. But the launcher seems somewhat broken (keeps crashing) so I wonder if on the old system it was also the launcher causing the bootloop. Anyway, I have lost my data but have a working system again for now.