Table of contents
Textures

Polyhaven
Texture Haven is 100% financed by donations which is the reason there are no limitations. All textures are available in 8K which is more than enough for almost every project for every texture there are AO, Diffuse, Displacement, Normal and Roughness Maps available. The only problem here is that there are only 151 textures available but this will hopefully change soon.
Pricing: Free

3dtextures.me
3dtextures.me also has a big variety of textures. all made with Substance Designer. Which means all of them are seamless. But to download them in 4K you need to become a Patreon. as a free user, you can only download them in 1K which maybe is not enough for some projects.
Pricing: 1K Textures Free 4K Textures starting at 5$ per Month

textures.com
textures.com has by far the biggest selection of Textures and gets used by the biggest studios around the globe. They are also offering not only textures but also 3d scans and objects. But you need to have a completely free Account. But to download textures in bigger resolutions you need a Premium Account.