If all you need is time tracking, Kimai2 and several others will do the job just fine. But I've found in my line of work that it's useful to be able to produce formal quotes and invoices for tracking purposes. Ninja lets you do all of that, no extensions or modules required, and all of the components are integrated with each other (quotes can be converted to invoices, projects, or both, invoicing can be done by task or by project, expenses can be included in invoices, etc.) and it also features a very nice automated emailing system for client invoice/quote notifications and even a guest frontend for them to log into.
So all in all, I've found InvoiceNinja to be extremely useful and can't recommend it enough.
Conversely, Synology Photos (which I use instead now) has a fantastic mobile app. However, if you really want reliable and granular object/face recognition, the Syno app is a little bare bones. It does some face recog but that's really it. However, its backup feature is reliable and I don't have to worry about if it's working in the background or not. I tried Nextcloud's photo plugin for a while too, but its mobile app had issues and I just couldn't rely on it.
Another project I've been keeping my eye on is immich: https://github.com/immich-app/immich
I'm happy for now with Syno Photos but it would be nice to have my photo app in my container environment with everything else I run and just use the NAS for media storage like I intended to.