This is a summarized guide I created while installing Firefly-III in a Proxmox (6.2-15) container running Ubuntu 20.04.
This guide has everything I did in one concise summary. Not much is explained. This will take about 1.5 hrs.
Note: I initially followed the official instructions and used a LAMP stack. I had issues with apache and getting the webserver to work (likely because I am not familiar with apache and am more comfortable with nginx).
To begin, first read through the two tutorials and official documentation so that you hav an idea of whats going on