I use rclone's encryption feature a lot, which allows me to put my stuff anywhere. Right now, I use a Wasabi S3-ish storage that is entirely encrypted with information only I know, meaning Wasabi doesn't even know what's on their servers. With that, I can mount this storage on Linux and Windows and I plan to drop my backups there as a third location in my backup chain.

That said, rclone is a command line tool and doesnt have that many GUI tools. There is RClone Browser, which is good, but certainly not the be-all-end-all of GUIs. But it get's the job done.