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've been running Seafile for over ten years. They released version 12.0 just last month. I'm really not sure why people have this impression that it's not maintained.
Seafile updates slowly because it's very much intended as an enterprise product. It has minimal bells and whistles, but the core functionality is reliable and works well. It's more of a BlackBerry than an iPhone.
In the side by side tests I've seen it syncs a lot faster than Nextcloud. I keep my entire documents, downloads and picture folders synced there across three different machines, nearly 300GB of data in total, and I can wipe my laptop and sync all my files back in under and hour. File transfers basically cap out at network speed, even with large numbers of small files. I've used the desktop client, the drive client and the mobile client and never had any complaints with any of them.
Sidenote, if you create an account on their site they'll give you a pro license for up to three users, free forever.
The documentation is a bit of a beast, but worth reading thoroughly. Setup is a little fiddly compared to Nextcloud (that's a major turn off for a lot of people, understandably so). If you have questions message me and I'll try to help. If you go with the free pro license, be sure to enable offline garbage collection, it'll help keep your storage use under control.
Anyway, I really like it, works well for me. Definitely worth trying out.