I ran OwnCloud for a while, until that project died. I liked that it focused on file sharing/syncing only. Reluctantly migrated to NextCloud and it's bloated beyond belief. It works though, and I've been too lazy to look into alternatives.
There’s OCIS now, which is a very good alternative if you’re only looking for a file sync solution (without all the App platform aspects of Nextcloud)
Enterprise focused software written in a meme language. Not interesting.
There are plenty of things to not like about Go, but it's certainly not a meme language. It's one of the first languages I'd personally seriously consider if I were to write server-side file sync software. (PHP, on the other hand, would be way far down on the list.)
How about you give it a try first? It uses about 1/4 of resources as Nextcloud in my experience, is a lot faster and has a way nicer UI.