I've played around with many self-hosted file manager apps. My first one was Ajaxplorer which then became Pydio. I really liked Pydio but didn't stick with it because it was too slow. I briefly played with Nextcloud but didn't stick with it either.
Eventually I ran into FileRun and loved it, even though it wasn't completely open source. FileRun is fast, worked on both desktop and mobile via browser nicely, and I never had an issue with it. It was free for personal use a few years ago, and unfortunately is not anymore. But it's worth the license if you have the money for it.
I tried setting up SeaFile but I had issues getting it working via a reverse proxy and gave up on it.
I like copyparty (https://github.com/9001/copyparty) - really dead simple to use and quick like FIleRun - but the web interface is not geared towards casual users. I also miss Filerun's "Request a file" feature which worked very nicely if you just wanted someone to upload a file to you and then be done.