I had a similar setup with Twilio, I switched to using Signal via signalbot framework. It’s a fairly straightforward process and it runs on my Pi in a docker container.I can even send it attachments and it will archive them for me. Sky is the limit.
Mine runs in the background when I get home. It uses an iBeacon device to determine when it is home. It starts the photo sync in the background. If I take photos and want to sync immediately I do that by starting the sync in the app. Remotely is a two part process —- enable vpn, then sync.
iCloud backups of photos is possible without using iCloud. I use a photo syncing app on my phone that is paired with a SMB server in my home. It just dumps new photos whenever I’m on my home network. But I don’t get iCloud syncing photos to my Mac instantly.
iCloud backups of device backups requires a Mac, then setting to sync via Wi-Fi.
https://pypi.org/project/signalbot/