Synchronizing data, files between devices should not be a pain. IN the past I used to do it via rsync, sshfs and other shenanigans
Today I simply use syncthing which is a self hosted selfcontained app which you can easily configure on many devices.
Once the devices are up they synchronize the state. You can exclude various folders.
Your own synchronization server at home with Raspberry PI
The neat thing is that you can even buy and setup a raspberry pi with a dynamic IP and DNS at home. Configuring it with an external HDD/SSD and you’ve got your own cloud environment.
All you need to do is run synching on your raspberrypi and you’ll automatically synchronize all your devices!
Theoretically you could plug in 2 HDD’s and run a backup script on the 2nd HDD in case your main HDD crashes.