Here are some extra references:
- Amazeen, Étale and Pro-Étale Fundamental Groups;
- Belmans, Grothendieck Topologies and Étale Cohomology;
- Bergström--Rydh, Étale Cohomology Spring 2016;
- Conrad (?), Étale Cohomology;
- Hajj Chehade, Sheaf Cohomology on Sites and the Leray Spectral Sequence, Chapter 3;
- Klingler, Étale Cohomology and the Weil Conjectures;
- Kunkel, Étale Fundamental Group: An Exposition;
- Laskar, Étale Cohomology;
- Puttick, Galois Groups and the Étale Fundamental Group;
- Robinson, Étale Cohomology;
- Sarlin, The Étale Fundamental Group, Étale Homotopy and Anabelian Geometry;
- Szamuely, Galois Groups and Fundamental Groups, Chapter 5;
- The Stacks Project Authors, Étale Cohomology;
- Yang, Fundamental Groups of Schemes;
- Zarabara, Étale Cohomology over $\mathrm{Spec}(k)$.