Encryption lengths are getting long so you’d think it was high time.

that’s unrelated - AES-256 for example can be executed just fine on either a 32- or 64-bit machine. in theory there’s nothing stopping you from running it on an 8-bit or 16-bit CPU (although other considerations related to the size of AES’s lookup tables make this unlikely). from some random googling, here is an implementation of Chacha20, another 256-bit encryption algorithm, for 8-bit microcontrollers.

when we talk about 32 vs 64-bit CPUs, in general we’re only talking about the address space - the size of a pointer determines how much RAM the computer is able to use. 32-bit machines were typically limited to 4GB (though PAE helped kick that can down the road)

CPU registers can also be sized independently of the address space - for example AVX-512 CPUs have a register that is 512 bits wide even though the CPU is still “64-bit”.

it might be more complicated than you’re looking for (requires a self-hosted server instead of just a desktop app), but take a look at the ecosystem surrounding Subsonic

Subsonic did some licensing shenanigans, but there’s an actively-maintained GPL3 fork called airsonic-advanced

there’s also alternate implementations, Gonic and Navidrome, that maintain compatibility with the original Subsonic API

because they all work with a common API, there’s a variety of clients that can work with the backend.

I’m also a big fan of Beets for music organization, it’s not tied in to the Subsonic ecosystem so you can use them completely separately if you want. it handles tagging, can fetch lyrics, and can also transcode the library (or an arbitrary subset of it) if you want to send it to a portable device. (not sure if this is what you mean by compatibility)

I currently have Beets organizing everything, run Navidrome on my server pointed at the Beets library directory, then Ultrasonic on my phone, and the Navidrome web interface on my desktop. the combo is especially nice for streaming to my phone - Navidrome will transcode FLAC to Opus on the fly, and Ultrasonic has an option to cache those files locally, and to pre-download them over wifi instead of mobile data. so I have my full collection available on my phone, can stream it from anywhere, and the songs I listen to frequently are already downloaded and I don’t have to waste mobile data, or wait for them to load if I have poor cell signal.