One trick, even though it doesn't "lock it down" the same way, is to use a minimalist launcher. Check out OLauncher. It is a text-based launcher, it only has room for a few apps on the homepage, and it discourages fiddling with your phone.

https://github.com/tanujnotes/Olauncher?tab=readme-ov-file

https://github.com/tstromberg/quietude is how I manage my Pixel phone as well as my kids; I begin with “quietude.sh disable all”, but usually re-enable maps.

It takes a similar approach to the OP - changing restrictions requires a USB cable and a computer.

andoff[1] works well. I use it to lock down DNS settings to nextdns to block all the sites I want. Then I use lockmeout[2] to lock opening andoff to change the settings.

Also there is limitphone[3], but it has less settings and is easier to uninstall than andoff, but works via the same mechanism.

1: https://docs.andoff.one/ 2: https://www.teqtic.com/lock-me-out 3: https://limitphone.com/

On LineageOS 22 this is what I did:

* Remove Jelly browser with `adb shell pm uninstall --user 0 org.lineageos.jelly`

* Disable F-Droid so you can't install another browser on a whim with `adb shell pm disable-user org.fdroid.fdroid`

Author here: I think so! A reader shared with me that they used the adb cli to remove all the apps they didn't want, including the Play Store.