Try out Poweramp, I would disable network access but otherwise this is gonna be hands down the best in my opinion. It's a premium option though, you'll have to pay to use it eventually but let's you use it for like a month or two for free. Can buy it on their website and then they'll give you an apk to download so no google services needed

Otherwise, on F droid I really like Lotus music player, looks super nice and works well. Def suggest this one as well and of course its free, so even better