Unfortunately, there doesn't seem to be anything better than Calibre at the moment. (Though, I'm happy to be proven wrong!) Nothing against Calibre, it's functionally amazing free software and it works very well; I said "unfortunately" because the interface is extremely dated and clunky and confusing to operate. Once you get it working, it's very nice though. As long as you never have to go fiddling with it again, because every time you've gotta reacquaint with it's weird UI. Still, it really is the best available at the moment, and it's free so that's awesome.
My favorite way to set it up is using the linuxserver image, which has a web-based VNC built into it, so you can remotely run the app on a headless server and then use your browser to interact with it.
I have Calibre configured to monitor a folder for new stuff I throw into it, where it'll automatically fetch metadata and put it into the database. Calibre also has an OPDS server built in, to which I point a nicer frontend for reading comics. Currently that is Kavita which provides a decent web UI for both books and comics.
Anyhow, I believe you could enter data about your physical comics into the Calibre database, and then view the metadata with something like Kavita, though of course you'd be skipping the reading features.
Thanks for the suggestion, but it seems like the challenges with Komga would be similar to those when using Mylar. I'll probably just go for a spreadsheet.
I use Komga + Komf for digitals but seems like you could do simply with mylar without a download agent. Might need to create a dummy file for each issue you own to change status to owned. Been ages since I have used so not sure.
That was my first idea too, but last I checked it didn't scrape much other than English editions (using Comicvine AFAIR) and had no way of manually adding stuff it can't scrape.
Yeah. Komga + Komf seems like overkill for your use case too. Komf would definitely get around the limitation of english editions only.
Readarr can track comics/manga too but unless you're interested in only indexing by author I have found it less than ideal.
Tachidesk or sorayomi or whatever they are calling it now may be an option? Like the other tools I have mentioned it's primary function is for piracy but I don't see why you couldn't just add sources and add series to library without downloading. Again would need dummy files to track owned vs unowned.
For your comics list, I'd suggest Dataview, quickadd, and templater plugins. With those three you could easily make a database with an entry mask, that automatically sorts the files into folders and sets metadata based on the mask input, and dynamically creates various tables for reference.
Folder notes could be useful too, depending how you want to set it up, and how detailed you want to have your tables.
Hmm could you use something like https://www.kavitareader.com/ and for items just add a single title image of the comic (with real title ect). So it shows up in your list?