Notable competitor: Arq (https://www.arqbackup.com/). Part of the reason I prefer Arq is that there's no monthly fees on the tool itself. I own my backup data wherever I choose to send it to (S3, Google Cloud, etc).
Also, Relica can back up to multiple cloud services with just a single upload of your data, whereas I believe with Arq it's one upload per cloud destination, lending itself to up to 5x faster backups. This is through our Relica Cloud destination which is optional for all users.
Relica technically already supports "bring your own cloud" (your own S3, Google Cloud, SFTP, etc - many others) but is still undocumented as we finish its implementation in the UI.
And your Relica membership can be made essentially free if you refer just a few people each year.