In the meantime you could use LineageOS (without or with GApps that you need to flash just after having flashed LineageOS if you want to install them for notifications for instance. Pico is a good choice).
But yes it’s possible to reinstall the stock ROM :
- Select your model and your country,
- Click on the one you want to download,
- Click on Join to download and create a dump account,
- Return to the previous page and the Join to download will be replaced by a Free download (or something similar),
- Click on it and wait around 1h30 for the download to complete,
- Unzip the zip file you downloaded,
- Go to this HOWTO at the “4) Download ODIN” and follow the steps then go to the “6) Install TWRP” part, you don’t need the 5) part,
- Follow the steps but instead of selecting TWRP, select the file that was inside the zip file you downloaded,
- You can stop reading once you reach the “WARNING :”,
- Your phone should start on the stock ROM, wait a few minutes.