FilaMeter is a free, open-source (CC-BY-SA-4.0), local-first spool inventory you run in your browser, a nice fit if you want a private, no-login spreadsheet replacement for a single hobbyist and don't mind logging usage by hand. It's a young 2025 indie app; it doesn't connect to printers and has no filament database yet.
SimplyPrint is a connected filament manager that has been running print operations since 2020: it reads the G-code of every print on your printer and deducts filament automatically, with native NFC, Bambu and Creality AMS auto-import, the open, MIT-licensed Open Filament Database (143 brands and growing, the very database FilaMeter is only planning to adopt), native iOS and Android apps and cloud sync by default. And the filament manager is free on every plan. If you want tracking that just happens, that's SimplyPrint; if a private local log you keep up by hand is the point, FilaMeter is a fine, cheap pick.