I have the same problem with one of my two Seagate 8TB USB drives. Both are connected to mi M1 iMac via an ANKER hub. The drive I use for TimeMachine has no issues. The other one I use for media files keeps popping up the "Drive Not Ejected Properly" message every time the computer wakes up. Per Seagate suggestions, I checked the cables, switched ports on the hub, set the energy settings to "Prevent you Mac from automatically sleeping", not "Put hard disks to sleep", and "Wake for network access". I also repaired the drive which needed repair. Seagate suggested that the not ejected warning would pop up if the disk needs repair. The disk did need to be repaired. This worked fine after the first awakening. Then it resumed popping up the notification. It turns out that the disk needed repairing once more. Any suggestions?