I hope you got this sorted, but for anyone else who struggles and your old phone still works, this is what I did... I hope you can tweak this to work for you.

I use an app called x-plore, you can get it free from the play store, I'm sure there are alternatives but this is what I use, and it's a great file manager. It has some pop-up ads but not videos and you COULD pay for it it irks you.

So anyway, open up x-plore.

The general idea here, is that we need the APK file from your old phone, on to your new phone. I have a network file server so I coppied the APK file there. If you don't have this. I suggest you copy the file to the 'Download' folder on your phone, then USB plug your phone into a PC/Laptop to copy it off, then plug your new phone in.

If you're really fancy about it, you might be able to copy direct to your new phone, but I am not fancy and I wanted the APK file to backup somewhere since it's not on the play store.

So, open up X-Plore on your old phone, swipe so you are viewing the left side if you aren't already. We can think of this as the source. Browse to App Manager > Installed and find Muzecast.

Now swipe to the right, this will be your 'target' and choose a suitable location you want to copy the file to. If you are unsure, chose Internal Storage > Download. I selected my File Server.

Now swipe back left, press + hold Muzecast app and Create Zip. This will copy the APK folder from 'source' to 'target' as a zip file. The zip should only contain the APK file.

Next, what I did, was unzip the file on my home PC via file server , then used x-plore to download the APK file on my new phone, then open + install it. I was prompted to allow x-plore to install apps on my behalf and it all worked.

If you chose to copy to Internal Directory > Download folder, you need to plug your phone into a PC/Laptop and copy the zip off. Unzip it, then plug your new phone in to the same laptop/PC and copy the APK file. On your new phone you can use X-Plore (or probably just File Manager) to browse to the APK file and click it. It will probably tell you you need to allow some setting to do so, follow it and allow, then install. You should be bale to launch muzecast and login.

I'm no expert with android, but I can try and help if anyone has any issues.

I can also provide my Muzecast APK file if you struggle as well, but I understand it's concerning to receieve APK files from a stranger, hence detailing how you can do it yourself.

If you're unsure, you can probably google some much better guides on how to do this!

Good luck!