Yeah, I don’t actually recommend buying airpods unless you got them for free if you’re an Android user (that’s the only reason I’m using airpods atm).
As to open source, I believe CAPods is, unless you’re referring to an open source app for most headphones (which upon second thought you probably are).
As to that question, CAPods, according to their GitHub page, supports a few Beats devices, this app for Galaxy Buds on Windows/Linux devices, and this one for Huawei Freebuds device(s?).
Overall, the closest I could find was GadgetBridge, which has support (partial or full) for a few Samsung devices, one Nothing, a few Sony, and Bose(?), though, I did keep running into internal server errors, so it might be out of date.