@pizzawithana, after my last installation attempt succeeded, I didn't install any updates or anything. I brought it to a local authorized Apple retailer for a trading-in with a new MBP. I got something like 728 euro discount for my old MBP (which was the maximum taxation value of that type). I too had a hard time doing this, since it was in otherwise perfect condition. I also hated it because I had to get a 2019 MBP, because there were no new ones in 2020 and the 2021 hadn't even been announced yet. I wished that if I would get a new one, I got one from current year rather than one from 2 years ago. I'm glad my post was helpful to you. Alternatively, if you don't want to trade it in or if you want to wait for the new MBP, you can try to install Windows on it and see how that works out (I have no experience with that).