They show no password prompt for the user with the “active” session for removable drives. Only system drives always require admin auth for formatting and partitioning. Maybe your session setup is not completely correct so your user session is not marked as the active session or you tried it with a drive that is considered a system drive.

I mean the exact same 2.8GB file, with the exact same USB-C stick took FU***** 3 seconds on Linux !!

For that test you should run sync afterwards to make sure the file was really written and is not waiting in a cache.

It is possible to format removable drives without root access through udisks2, e.g with gnome-disks or KDE ISO image writer. GNOME Impression is another tool that should work.

Curtail is a wrapper around tools like pngquant, jpgoptim and oxipng. In lossless mode it optimizes and reorders e.g the compression tables. I know of no tool that does that for video data and I am not even sure that is feasable. Video is not stored as a simple sequence of images.

Sorry, I have no idea.

The relevant polkit policies should be defined here: https://github.com/systemd/systemd/blob/main/src/login/org.freedesktop.login1.policy

Disabling is done with some rules like this: https://bbs.archlinux.org/viewtopic.php?id=152565

polkit.addRule(function(action, subject) {
  if (action.id.indexOf("org.freedesktop.login1.power-off") == 0) {
    return polkit.Result.AUTH_ADMIN;
  }
});

Some other examples: https://gist.github.com/grawity/3886114

Is it common for cups to run as root? It should have its own user, but that is still not good.

Hmm, never had cups-browsed enabled as I do not need network printing with LDAP or legacy cups. Discovery using DNS-SD/mDNS and driverless printing work perfectly fine without it.

I am not sure if the driverless discovery ever can generate a PPD with arbitrary commands.

For Linux maybe timekpr-next and some custom scripts to sync the time with the time limit server?

ReactOS is probably a good indicator how far you can get with some limited generic drivers.

As a CLI there is gifsicle or imagemagick.

As a gui maybe gifcurry, tupitube or some other 2d animation tool https://en.wikipedia.org/wiki/List_of_2D_animation_software