It's very depending on which apk you want. If you only want the apk of one specific open source app, just check on fdroid or on their git (mostly on github). And if you want play store apps without installing Aurora store, just use ApkMirror (their apks are mostly clean, cleaner than Apkpure in any case..).
Meta train open llms, only big techs can train AI... Go pursuit OpenAI or Google and leave Meta (I'm really not a fan of Meta but their "open" AIs are great examples of good works) do their work!