I'm holding off on upgrading to Android 11, but there is an AIMP public beta version you could try. You can get the either get it through the Play Store, or sideload the beta APK off of the official website (aimp.ru).

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Works perfectly for me as well as it's windows variat too. It may not be as intuitive, but it's beyond rich in features if you're savvy enough to learn. More on reddit.com

AIMP is simply great More on reddit.com

inb4 thread ender: PowerAMP (PAID with FREE TRIAL), best one I've tried, has software audio processing, might be placebo but I could swear the sound is different compared to other music player even though same device and same files. Has its own design language, but looks very nice. Poweramp is also the only one that has visualization react to the song's beat and has support for .milk presets (Winamp visualization files). other notable offline music player to try Neutron Music Player (PAID), it sounds hella good, something to do with software audio processing? but it's so fucking expensive and has a UI design only its mother could love. Musicolet (FREE with PRO extra features), the go-to recommendation for totally free music player, has all the features you need and more Oto Music (FREE), well designed offline music player, simple looking, material you design. Shuttle 2 (TRIAL), the app itself is free but after the trial ends, it'll increase playback speed step by step lol, one of the most creative "buy the pro" I've met. GoneMAD (PAID), you can have the trial version first and pay for the unlocker if you like it. BlackPlayer (FREE & PAID version), simple design, very cool, but hasn't been updated in some time VLC (FREE), a video player but also support audio, personally not a fan of mixing media player like that, but hey if you like it you like it Retro Music Player (FREE), paid for extra themes, I think the development has discontinued? still, it's a pretty good looking music player app Stellio (FREE), with paid unlocker like Poweramp and GoneMAD, also one with their own design style, not following material guidance, looks pretty nice imho. USB Audio Player Pro (PAID), the only one I haven't tried, it supports DAC so if you know what that means, maybe it's worth it for you. Simple Music Player (FREE with a DONATION option as separate app), by Simple Mobile Tools who also made Simple Gallery, Simple File Manager, and other Simple Apps. Lacking features and the design can be too simple, but hey it works. I want to recommend some open source players too like Phonograph Plus, Vinyl, Mucke, Auxio, and Metro, but they're all either kinda lacklustre or just doesn't offer anythiing extra, at least they're free to try, though some even crashed on my phone. why do you want alternative for AIMP ? is it not good enough? EDIT: added more apps and contexts. More on reddit.com