Well, it works in a different way than NextCloud. You don't have a server, instead you just make a share between your computers and they are all peers.

It takes some getting used to the idea, but it's actually much simpler than NextCloud.

It really wasn't all that complicated for me. Install the client on two devices set a share up on one device go to the other device Hit add device put the share ID in. Go back to the first devices admin and say allow the share

I was very intimidated as well, I'll try to simplify it, but as always check the documentation ;)

This is the process I used to sync between my Windows PC and Android phone to sync retroarch saves (works well, would recommend, Pokemon is awesome) I've never done it on a Linux, though i assume it's not too different

https://docs.syncthing.net/intro/getting-started.html

I downloaded the Synctrazor program so that it would run in the tray, again I'm not sure what the equivalent/if this would be necessary on Linux.

No shade to the writers, but the documentation isn't super noob friendly, as I figured out. I'd recommend trying to cut out all the fluff, and boil it down to bare essentials. Download the program (whichever one seems right for your device, there's an app for Android) and follow the process for syncing stuff (I believe I used a video guide, but it's not actually as complicated as it seems)

If you need specific help I'd be happy to answer questions, though I only understand a certain amount myself XD