I‘m using calibre with calibre-web [1] to browse my 80000+ pdfs and couldn‘t be happier with the workflow. Only downside: import of these pdfs took almost a whole day.
Autocompleting metadata automatically from Amazon Books is also great. Plus multi laguage and multi user function. As well as collaborating on public shelves to create useful collections. I also let my co-workers and friends upload ebooks.
It's great.
Do you know if and when they migrate calibre-web to calibre 5? I don't know if the project is active.