I have actually setup nextcloud on a Synology NAS and it's rather straight forward. Also keep in mind that a shell is scary to some and for good reason. I would not advice anyone who does not know what they are doing to do something through a shell.
That is indeed correct so if you
@OnePieceLuffy feel overwhelmed at the installation. Either get the knowledge needed or find a different way to do it. If things go awry you'll thank yourself!
@OnePieceLuffy: If this seems complicated I would stear away from this and go for a docker image
https://hub.docker.com/_/nextcloud I think TrueNAS has the ability to run dockers if I'm not mistaken. This guy has a video on setting it up (docker that is) I watched a few of his other movies and he seems to know what he's doing:
https://www.youtube.com/watch?v=XBVjuwgz0Cg