Thanks to my lovely textile colleague Sarah Goslee, I've been pointed to the DOAB - the Directory of Open Access Books. And yes, it does contain quite a number of textile-related books!
You will probably have to filter down if you only search for "textile", as there's a lot about modern speciality textiles and modern textile manufacture in the list, but fortunately an "archeology" filter exists, as do several others.
You can find the main directory at https://www.doabooks.org/en. I hope it will be helpful for you!