I don’t know about AMD, but nVIDIA drivers have this built-in. Just open the nVIDIA control panel, go to ‘Adjust desktop size and position’, and then under the scaling tab click Integer scaling.
It’s great for old super low resolution, 2D games, but that’s about where its usefulness ends. It’s not going to make 1080p look as good on a 4K monitor as it does on a 1080p monitor (where you’ll probably have better luck using anti-aliasing combined with nVIDIA’s image sharpening). It’s not a replacement for DLSS where you can legitimately render a lower resolution with limited loss in image quality.
Also keep in mind that since it’s integer scaling, it’s not going to fill your screen unless the game is running at an integer of your native resolution.