So I became aware of this app called Bluebubbles a couple of weeks ago. It’s a bit of a workaround but it allows you to iMessage from an Android phone. In addition to running the app on your phone you need to install the server app on a Mac. The Mac needs to be always on and always awake. Your iMessages will be sent from your email address rather than your phone number. There are workarounds to get it to work with your phone number but those involve using an iPhone and are a bit flaky (eventually iMessage figures it out and your phone number gets dropped). I’ve been experimenting with it for a week or two and so far it’s working well. I’ve got the software running on a 2014 Mac Mini that I picked up a while back for under $200 shipped.
https://bluebubbles.app/downloads/
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