Linux

uhm, well you can't primarily because android is a hot mess (quick note: this is mostly me ranting about the hell that android is for no fucking reason)

First of all, android only supports MDNS since android 12 and newer, MANY years after the standard was even finalized and put into use. (like a concerning amount) And yes, you can technically use that networking on a per app level (since android 6 or 8 i think), if it's implemented, but most apps don't because they're android apps. And the ones that do are basically useless (very cool thanks android)

Ignoring this, let's say that you have a samba server, and have a local DNS config setup to get around the MDNS bullshit. Oops, funny story, android doesn't natively support SMB shares, because apparently they aren't real and don't fucking exist. Now to be clear, most file managers do actually support SMB, the problem here is that those are often shit, and only supported in the actual file manager itself. If you wanted to per se, mount a samba share on android on the FS level, it is either impossible, or REQUIRES ROOT ACCESS.

Man it's a good thing rooting is easy, and not super convoluted, or risks bricking your phone in the event that it's designed like utter shit and cannot recover from being flashed incorrectly. (to be clear, i don't know shit about rooting, because it's a fucking disaster, and i might be misrepresenting it here, but only rooting, everything else is accurate)

so basically, cool story, the only option here that you have is using apps that are specifically designed to implement their own file transfer functionalities and protocols. There is one redeeming factor to this, and it's the fact that rsync exists, and that it isn't shit, but rsync isn't samba, so eat shit android. Rest in piss you disaster of an OS.

snapdrop.net

There are some browser based solutions like sharedrop.io and file.pizza. I haven't had the latter work for me though, not sure if it's still functional. They work through WebRTC to discover local candidates for receiving files, the same way that video calling typically finds the best connection.

Security

ShareDrop uses a secure and encrypted peer-to-peer connection to transfer information about the file (its name and size) and file data itself. This means that this data is never transfered through any intermediate server but directly between the sender and recipient devices. To achieve this, ShareDrop uses a technology called WebRTC (Web Real-Time Communication), which is provided natively by browsers. You can read more about WebRTC security here.

I use kdeconnect with this script: https://github.com/Samueru-sama/kdeconnect-any-filemanager

Simply install flatpak then install warpinator

snapdrop.net if on the same network

I use Airdroid! It's free and works very well

samba. share a folder on pc, and on your phone use a file manager that can access smb folders in your local network, then just copy or move from or to that folder. bit of a hassle to set up the first time, but makes things more convenient in the long run.

Mostly because I'm not the most competent techie, I've been using VLC between my PC and iPhone, for moving "books" around on devices that are very out of date.

Croc or syncthing depending on what kind of experience you are after. Syncthing if you want to have a shared folder like expert. And croc if you just need to send something. Croc has an app on f-droid, and syncthing is on the app store. Both are open source and pretty for excellent in their own right.

X-plore on android can give file access via Web frontend in paid Version.

With that you can drag and drop files if that's what you're looking for.

wifi file explorer pro apk

My go to hack was quickly running a python http server and connect to it. I can't remember what the command was exactly. Something like python -m http.server or so, then connect to the ip from my phone, heh.