What is the best or recommended way to integrate my Windows 10 and Linux computers through the local network?

There are currently four computers in my household: a Windows 10 desktop, a Windows 11 laptop, and two additional Linux laptops (those are "mine"). One is a very weak but new machine, basically the cheapest laptop I could buy that was neither Android nor literally a toy. It is running Lubuntu 24.04, and is used largely for writing and light browsing. The other is an older machine running MX Linux. Right now it's single purpose is running my Plex server. Given that setup, transferring files between machines is often a necessity.

Both my desktop computer and my Plex server are connected via Ethernet directly to the router. The other two laptops are connected largely via WIFI, although I do connect my writing laptop via an USB/Ethernet adapter for updates/upgrades and larger downloads when necessary.

Among other things, I often download movies on my Windows 10 desktop computer and then manually transfer them in batches to my Plex external hard-drive, and then to my Plex laptop (when it has enough space, otherwise I just keep the movies on the hard-drive). That is because it is way more convenient for me to (re)search what I wish to wwatch, find and download it to my desktop than it would be the case for my Plex laptop. The laptop is not only in a position that makes it uncomfortable to use but is also very slow even for basic things such as firing up Firefox. I also prefer to do the scraping using MediaElch and while it is a fairly heavy (probably Electron) application, my desktop is powerful enought that it doesn't make any diference. I also use Subsync sometimes, which is, as far a I know, only available as a GUI application on Windows.

Most content I find online is very practical, teaching me how to follow concrete steps to make things work, but I haven't found much advice on which programs or tech "stack" would be adequate for a specific situation such as my own. I just want a robust way to seamlessly transfer file between all the machines on my home without having to plug and unplug hard-disks and flash drives.

Any suggestion? Thanks!