I'm using it with Scaleway Object Storage (S3) and it works great. Tho, not sure why it is specifically stated as for "DO Spaces or AWS S3". It should work with any S3 storage system. No difference for the changes you need to make in the PHP codes.
I love this add-on, works as expected
But there is a note you should know, if you want to disable this add-on, you should remove the code in config file before click disable add-on
It's been almost a year I don't see add-on update, I hope Chris D could update it (if it needed to improve)