I found the easiest way to sync is to use rclone. This way you can use any cloud provider like Google Drive or OneDrive or DropBox. First create the rclone remote for your cloud provider using rclone config. Second step is to create a second remote using the encryption option (menu item 16), choosing an appropriate path <first remote>:<path to directory>. Upload your KeepassXC database to this encrypted remote using rclone copy.
On Android you can use the RoundSync app from F-droid to configure the the same remotes, then create a task to copy or sync from that encrypted remote and a trigger to run that task on a schedule. Overall, this one-time setup works really well for me. This is my backup in addition to using Bitwarden for several years. Bitwarden is not going to get my money any more.
Rclone with any cloud provider is another great option that's seldom mentioned. I posted my setup as a comment on another post. You may find it here - https://programming.dev/comment/23849767