Let's use this thread to gather links for other cool resources! I'll go first, here is a list of really good trifold templates:
https://gontijo.itch.io/coolrpgpamphlets by Guilherme Gontijo
https://emosludge.itch.io/3d-trifold-template by Zach Hazard Vaupen // Emo Sludge
https://brstf.itch.io/a5-pamphlet-affinity-template by Brian Stauffer
https://mr-matthew.itch.io/trifold-pamphlet-templates by Matthew Gravelyn
https://axolotl-jdr.itch.io/template-pamphlets-affinity by Axolotl