There are a lot of different methodes you could try. I think the easiest is to connect both systems with a (mesh)VPN like Wireguard, ZeroTier or Tailscale. Then you can simply copy stuff over using rsync -a (archive mode) with a cronjob or using special tools like Borg backup, kopia, etc
I use SplittyPie allot with my friends if we go on a trip/do something together. Works really well. You can install it as a PWA and it's FOSS ;)
n8n.io is great, but not open source.
I don't think there is an app for something like that, but maybe you can try using Penpot in a browser?
I use this all the time, also nice for text share.
Take out the hard drive out of your laptop and put the drive for the server in it, install Debian using the built in monitor and keyboard of your laptop.
I use this app on my Pixel 6 running GrapheneOS, or you can install the website as PWA
I use Deemon for automatic music downloading from Deezer (free). Then I stream my music with Navidrome and some Subsonic compatible apps for mobile. I have this setup for over 3 years now and I have 3TB of music ;)
If you just want to download the songs you need, you can use Deemix (I use this Docker image, you can just install it as an application too)
Tip: if you don't want to setup a music server, you can use Syncthing to sync you music and playlists between devices :)
RSS Guard seems to have support for Google Reader API, so FreshRSS is also supported. It's also a Qt application. You can also find other clients on the 3rd party clients page of FreshRSS
I use PairDrop allot for sending peer to peer files/text to other PC's on other networks. FOSS and can be self hosted ;)
I use deemon to download my music from Deezer (free account only supports 128kb/s, this is enough for me though).
For the music server I tried both Jellyfin with the Finamp app and Navidrome with the Tempo app on Android.
For desktop app for both I use SonixD/Feishin (crossplatform)
Both where fantastic solutions but I stuck with Navidrome as it was easier to share playlists. (As an URL for non registered users or as public playlist for all registered users)
My setup is as following: Hypervisor: Proxmox VE NAS: TrueNAS Scale (where all music is stored)
1 LXC container with Deemon installed that downloads music in mounted NFS share from TrueNAS
1 VM with Navidrome installed in Docker with the music folder mounted with NFS
You don't have to use such a setup, you can perfectly do this on your existing PC with Windows, MacOS or Linux with DE. Or server OS like Linux with CLI, OpenMediaVault, TrueNAS Scale or unRAID
And recently Llama3 and Mixtral!