I'm posting this topic for those who don't know how to do it, not to ask for help.

There are 2 ways to do it:

1. Installing these packages:

android-file-transfer
android-udev
gvfs-mtp
libmtp

(such are the package names in Arch official repo but they might be differently named for your distro)
and executing mtp-detect in terminal. Sometimes executing this command may not be enough (usually it is but depending on the distro, it may not be enough), in which case you'll have to reboot before the phone can be detected.

2. WiFi File Transfer Pro - an Android app for the phone.
Install it on the phone, run it and tap "start". That will enable a local address to open in your browser which will give you a wi-fi access to the phone. The only downside is that it only gives access to the internal memory but not to the microSD card, so if you wanna trasfer data from the SD card, you'll have to move it to the internal memory first. The app is useful for pictures, mostly. I haven't tried using it for music or large video files - for that I prefer method 1.

This is what it looks like in the browser: https://i.imgur.com/9BlkocT.png

When you're done with the transfer, simply press "Stop" in the app and that's it.

The Pro version of the program is quite cheap to buy - 1-2 euro, if I recall correctly. The Pro version has no file size limit. The regular version has a file size limit of 5 MB, I think.

There is also KDEConnect, which will link your computer file manager to your phone.

Discover kdeconnect.

Best thing that I have ever used for mtp. It just works. And simply.
https://github.com/phatina/simple-mtpfs/
https://aur.archlinux.org/packages/simple-mtpfs

Been using it for...don't recall how many years. Make a bash script for it. Not dependent on any DE/WM/File manager. Could use it in tty if you want.

The ways I mentioned will work no matter what desktop you're using, whereas your way will work only for KDE. To your surprise some of us don't like KDE and try to use parts of it as little as possible.

The methods I mentioned aren't desktop dependent either. For as long as you have Arch, method 1 should work for you, regardless of the DE.
I'll try that simple-mtpfs too but seeing how long ago it was last updated, I have my doubts about it. The last update was 2 years and by Arch standards that's simply ancient.

Actually KDEconnect works with other desktop file managers. Gnome has an extension called GSConnect that uses the protocol, so you don't have to install any KDE libraries.
GSConnect may work with Thuner also for XFCE, or you can install the KDEconnect app and it's dependencies to work in Thuner. Or you can use the command line interface.
You can even install KDEConnect on Windows and Mac.

It is probably the most universal app around to sync your phone to any computer.

There is also an Android application, Cx File Explorer, a very powerful networked file manager.

You can also sftp the files over to your linux machine by installing a sFTP client on the phone, I use AndFTP. Another option is to run a FTP server on the phone for the duration of the transfer, the best one I found is built into the File Manager+ app.

Finally, my favorite option is to install Syncthing on both the phone and computer. Once you do that the files will sync across seamlessly. I have it configured to only work when both the devices are on the same LAN but you can also sync over the internet.

I have transferred massive amounts of data between the phone and computer using the above methods. SyncThing is most seamless/userfriendly, AndFTP is a bit unreliable with large no of transfers and the transfers from File Manager+ work fine, just that they involve an extra step.

- Suramya

i have just been using the USB-c cable

KDE auto mounts the phone for me .

Sorry, but I'm not paying for an app to do what I can do for free. I can just plug my phone in, mount it, and copy files through the file manager with zero problems, and have been able to for years. And as others have said, KDE Connect works great (again, free), as would bluetooth transfer (free), and just emailing them (free).

Nothing (aside from KDE Connect) requires any apps on the phone.