When I commuted by bicycle, I used a quick-release seat post binder. When I parked the bike, I took the saddle and seatpost with me.
I was looking at e-bikes the other day and saw that at least two brands, Veloctric and Aventon have some impressive anti-theft features. These include Apple “Find My” tracking built in and powered from a battery separate from the removable bike battery, a Geo-fencing program which allows you to restrict the bike’s movement from your cell phone wherever the bike may be, and automatic wheel locking and motor disabling, again activated from your cell phone.
Or maybe take just the saddle and leave the seatpost?