Yes, as arthor mentioned it is supposed to be a self hosted tool. But since it's client side and just a bunch of static files in the end, I will soon be porting it for all major platforms as an installable using Tauri
It can merge any type of pages. Also, if there is bookmarks in your PDFs, then it also preserves it. There's also an alternate merge feature in case you want (:
Yeah I couldn't find a good place to put it lol