I am not very familiar with PHP nor Symfony. I set up a PixelFed instance from scratch as well and that uses PHP Larval and that experience did help some, but I'm not a PHP developer at all.
As for the experience, after I got everything set up, I can see where the lack of documentation caused me to get stuck, but if I were to try again right now while using my experience as a guide, I can imagine a "relatively" straightforward set of steps to set up.
The only piece that I'm still not 100% clear on are what are the optimal configuration values for the JWT tokens (.env only mentions one token, but mercure's Caddyfile mentions both a publisher and subscriber), and which daemons should be run under which accounts. There are a lot of pieces:
php8.2-fpm
nginx
postgresql
mercure
redis
...etc
Also, setting up the worker threads via supervisord was unexpected and only mentioned in that other issue raised on codeberg.
I've done my share of documentation in the past and have thought about editing the wiki, but due to work at the moment I didn't have the time to record all my steps down in detail for this deployment.
I do hope to have some time soon, though and might try to take a look at the wiki and do a "test" deploy again.
My personal preference, though, is to not use Docker so I also understand that can add a LOT of complications.
I'm happy to share anything specific if you like as well about the experience. I used it as a learning experience and ... I did learn a lot for sure.
As for difficulty - with the state of the documentation as it was when I tried, it was quite difficult. However, once you have all the correct pieces and software parts installed, the configuration isn't any more complicated I think that other platforms (Mobilizon, Pixelfed, etc). There are a lot of pieces to get running correctly, though and any documentation should probably focus on making the installation of those different pieces as easy as possible as well.
On a scale from 1-10 with 10 being basically imposssible, I'd say without documentation completed - 8
With documentation completed - 4?
These assume at least a basic level of comfort working with Linux and installing software like this, though.