I am currently keeping a Nextcloud instance for my day to day paperwork and emails, but I happen to use Syncthing for my long-term storage needs.
I've always had this need to be able to access my large Syncthing collection of files from my mobile phone without installing the Android client, since doing so would result in all the files on my main folder getting synced to the phone.
That's where Filebrowser comes in. It's a standalone, web based file browser with download and upload capabilities along with image and PDF viewing.
Once you start it up on the directory you wish to have access to it fires up a web service on port 8080 on the host your started it. Initially you give username and password as
admin and then you change it once logged in.
Keep in mind that this is a temporary solution meaning that after you finish up with your file management it's best to stop the process since it is yet another hole in your internal network that gives access to your files.
My whole on-the-go process for using this on my phone is as follows. I launch my VPN from my phone to my home server, I ssh to my syncthing container and use tmux to start the filebrowser in my most used directory with a simple bash script. Once that runs I open the URL on my mobile browser along with the port of the filebrowser server and voilà! Anything I need to view or download is available in an easy to use graphical interface that is quite capable to say the least.