Hey bros. I have been using Romm as a rom manager for about a week and it's very promising.

So basically if you have a server and lots of roms or romsets it allows you to centralize your rom collection and make it easy to browse and download from from any device. The manager has no issue dealing with lots of entries as you can see (I haven't imported everything yet) and is very easy to setup. If you have a large collection increase the scan timeout or you'll have to start a new scan every 4 hours. The scanner and hash analyser are fast but it's held-up by the artwork fetching as it avoids sending too many requests so you don't get blocked. It has overrides so you don't need to have an exact match to the directory names and you can freely exclude or include directories roms and platforms as you wish. It handles zipped roms just fine. It also differentiates siblings and rom versions and can group them up.
It also manages saves and BIOS files but it's kinda limited right now.
The manager auto generates collections based on theme franchise or game type so it's useful for discovery. It also doesn't make the mistake of not allowing you to disable them or mix them up with user collections.
It can also double as a self hosted game tracker/backlog with completion percentages tags and retroachivements integration.
The web app comes with emulationJS that allows you to play games directly in browser.
The account system is useful and manages saves and collections per user. You can choose to share those or not and restrict access as an admin.
The web app is very well done and fast.

There's playnite integration muOS integration and tinfoil for switch integration. There's also a desktop client a steamdeck client and an android client.