Hi @stiebs Welcome to the forum!
Thanks for the great info on what you did it’s very helpful.
I think you have to move the project to a subdirectory called passbolt but the root must remain /var/www/passbolt.
/var/www/passbolt/passbolt
The help site is currently missing mention of this but there is a PR Add mention of using fixed path in URL by garrettboone · Pull Request #89 · passbolt/passbolt_help · GitHub
… which mentions this post which has an NGINX example Passbolt install in a subfolder