As others have said, try to avoid any kind of DevOps if you can. But here's my strategy:

Monitoring - Loads of cron jobs pinging slack (monitoring disk, CPU, Network I/O etc), Healthchecks.io, TurboAPI, Nginx Amplify. Mostly built up over time

DB - Done entirely via migrations. Most of the time they are small migrations so I can do it by running the command directly on the instance

Deployments - GitHub actions to build a docker image (there was a prebuilt template). Watchtower then runs on my server to pick up the new image and that's then deployed automatically. There is no rollback system as I've not needed that so far (and 99% of the time you won't).

Backups - DB backup is done via a cron pushing to AWS S3 Glacier. The app code is stored on GitHub already so no need to back that up. Happy to share the script if you like :)