I’m not an electrician but I’ve been in a similar spot. If you have non computer stuff that has a ground prong, you can replace a two prong receptacle with a 3 prong GFCI outlet and not hook up the ground. You just need to lable the outlet as “No equipment ground”. GFCI outlets generally come with these stickers since it is a common retrofit. If you hook it up right, any outlet that is GFCI protected downstream could be replaced with a 3 prong receptacle without a ground and would have to be labeled “GFCI protected” and “No equipment ground”. Even though there isn’t a ground, you are protected from electric shock by GFCI. You shouldn’t plug a computer into an outlet like that since computers use ground to filter noise from their power supply and require an equipment ground. If you need an equipment ground, you would need to talk to an electrician.