If you mean the charging port , basically you can but you need to remove the old one from the motherboard and to solder the new one on it. You need skill for that. Anyway you can order one from eBay or some other site.
I think not no matter that both are 3500 mah of capacity. The S8+ the battey is taller and the S9+ the battey is wider. Just order original one from eBay for example or some local store in your country.
I had similiar problem like yours. Tryed everything but nothing worked. Only the USB option worked for me, but with using a usb stick 2.0 not 3.0 . I losted many hours trying with the usb stick 3.0, but nothing. So download the OS from internet and boot it on the usb stick 2.0 (16gb stick or more) and try again to boot the stick. I used balenaEtcher to flash the OS on the usb stick.
With that size of the screen 85” will be pretty impossible to find out. If you get lucky and find on some site it will be very expensive. It’s better to get a new one TV that rather buy a LCD display for that model. Too I believe that you will not find out :/ I checked anyway on some sites which I know and nothing.