I tried Nextcloud a while back and was not impressed - I had issues withe the speed of the Windows sync that were determined to be "normal" with no roadmap to getting fixed. I'm now planning to move off Windows desktop so that won't be an issue - so I thought I'd try again.
I went to nextcloud.com, clicked on Download-> Nextcloud server -> All-in-one -> Docker image - Setup AIO. This took me to the github README at Docker section. I'm already running docker for other things so I read the instructions, setup a new filesystem for my data directory and ran the suggested docker command with an appropriate "--env NEXTCLOUD_DATADIR=". I'm then left with a terminal running docker in the foreground - not a great way to run a background server but ok, I've been around for a while and can figure out how to make it autostart in the background ongoing. So I move on to the next step - open my browser at the appropriate URL and I'm presented with a simple page asking me to "Log in using your Nextcloud AIO passphrase:". I don't have a Nextcloud AIO passphrase and nothing I've read so far has mentioned it. When I search for it I get some results on how to reset it, but not much help. I could probably figure that out too, but after reading some more I found that Nextcloud requires a public hostname and can't work with a local name or IP address. I'm already running my home LAN with OpenVPN and access it from anywhere as "local" - I don't really want to create a new path into my home network just for Nextcloud.
I'm sorry - I know this sounds like a disgruntled rant and I guess it is. I just want to check that I'm not missing obvious things before I give up again. All I want is a simple file sync setup like onedrive but without the microsoft.
I would suggest looking at Syncthing. It's not perfect by any stretch, but it works peer to peer, without any kind of central host, ip or domain name requirements. You simply install it on the client machines, and they work out how to talk to each other over any available networks.
Beware changing the casing on your files or directories though, Syncthing was made entirely case sensitive, which does not play nice with Windows.
One very nice feature is that it does have an android client (https://f-droid.org/en/packages/com.github.catfriend1.syncthingandroid/), and it supports full background syncing to your local storage on the phone. Great for syncing your photos, but also music. You add some mp3's on your desktop computer, and by the time you've put on your jacket they're on your phone ready to listen to without any 'service' getting in your way.
A more advanced tip; Get a VPS somewhere in the cloud with cheap storage, and have Syncthing on it listening on port 443. That will allow syncing in more restrictive corporate settings, which often don't allow connections to port 22000. And it gives you a 'cloud backup' of your important files in one go.