What OS would you put in a bug-out drive?

So after a few weeks of waiting I'm looking again for a distro that works with Secure Boot enabled to install (frugally) in an external drive as an everyday carry sort of thing.

To give a little more context: I'd like to have a complete OS packed in an external USB / SSD drive to boot from and pass some time when I'm out with my work machine (that has Windows) for things like a long business trip or while waiting in between external visits.

(How can I do that? Well, I recently discovered that this machine can boot external OSes via USB due to what I can only imagine is a configuration error by my IT department. I can even disable Secure Boot and change the BIOS password!)

So that's the question: what OS would you put in a bug-out USB drive? My only limitation is this: the OS has to support secure boot with minimal to no effort. Yikes, I know. But having secure boot support saves a lot of the work in having to manually switch on and off the option under the BIOS settings every time you need to switch boot media (because Windows, apparently, won't run without it on).

I've already made some progress in reducing the friction between the two by making the hwclock not switch from UTC to local time, among other stuff, but the Secure Boot thing is the one that has been so far unavoidable.

So what OS would you use? Let me know in this post's Mastodon thread!