You can get free scan-based PBR texture maps in up to 8K resolution.

The asset library LotPixel made over 1,200 of its photogrammetry scanned texture sets available for free. The PBR texture maps include multiple real-world materials in up to 8K resolution. They are provided as JPEG files with diffuse/albedo, ambient occlusion, glossiness, height, normal, roughness, and specular maps.

The assets cover materials like asphalt, brick, concrete, metal, plaster, stone, wood, plastic, fabrics, interior and exterior flooring, and wall materials.

If you want more assets, including 3D models, decals, and textures in higher resolution, you should get a paid subscription, which costs $9/month for a Freelance subscription and $27 for an Indie one.

Get the free assets here.