How can I make automatic, full system backups of Ubuntu during normal use (like Macrium Reflect for Windows)

Timeshift is pretty powerful and is included in the Ubuntu universe repo.

Plusses:

• It runs in the background at a frequency you specify.

• It actually works ...I had been doing Timeshift backups for years, but had never done a restore until last week. It restored my system perfectly...but kind of reset my desktop environment...but that is what Deja-Dup is for. Between the two of them, it seems to cover most cases.

Minuses:

• You can't back up over the network. Backing up to the physical drive your system is on is kind of dumb...so this is OK for multi-drive systems but not so good for, e.g., laptops. For small single disk desktop systems I stick a 64G USB in the back and set Timeshift to back up to that.