linux-libre is harder because if you want cpu ucode plus hardware firmware support in general so that you can make your bad citizen hardware work, you'll need to add it out of the linux package.

Someone mentioned Guix as a gnu + linux distribution was hard, and in general that's true, but not because of linux-libre since there's a non official Guix repository providing non libre/free cpu ucode plus hardware firmware, see:

https://gitlab.com/nonguix/nonguix

The complex part of Guix comes from it being a inmutable distribution based on the ideas from NixOS, though it's not a fork from Nix since it's even based on Guile rather than the Nix language, but their packages and configurations are quite different than any other distribution, the same as its inmutable system and I believe on both reproducibility is a thing...

But bottom line, for Guix you can even get packages to make linux-libre work with your hardware provided you find the corresponding firmware in the non official repo, and in general (not just Guix) as long as you find the firmware somewhere else (not in linux-libre) you would be OK, and depending on your distro that might be a really hard task.

I use Artix, and though I haven't explored it yet, I've been wondering how hard it'd be to install linux-libre, and get the strictly required firmware from the AUR, perhaps it's possible. The package is actually offered from AUR:

% aur search linux-libre
aur/linux-libre 6.11.9-1 (+37 0.35%)
    The Linux Libre kernel and modules
aur/linux-libre-docs 6.11.9-1 (+37 0.35%)
    Documentation for the Linux Libre kernel
aur/linux-libre-firmware 1.4-1 (+3 0.00%) (Orphaned)
    Firmware files for Linux-libre
aur/linux-libre-headers 6.11.9-1 (+37 0.35%)
    Headers and scripts for building modules for the Linux Libre kernel
aur/linux-librem5 6.6.57-1 (+0 0.00%)
    The Linux kernel for Purism Librem 5
aur/linux-librem5-docs 6.6.57-1 (+0 0.00%)
    The Linux kernel for Purism Librem 5 (documentation)

I would argue they're not safe to use because they block security updates like CPU microcode in the name of absolute freedom.

Short answer is Trisquel if you like Ubuntu/Debian, Parabola if you like Arch, and Guix if you like frustration.

The libre kernel is a bit of a pain regarding wifi and bluetooth, and depending on your graphics card the drivers aren't going to run quite as well. You might need to get new a wireless card/usb, since there's only a few modern chips that work with it.

There's a list of distros on gnu.org that use the libre kernel by default, if you want to look at more options. PureOS is based on Debian focused on privacy and security. Hyperbola is based on Arch with 32 bit and BSD options.

Personally I use Guix, which is an amazing abomination with awesome features that most people don't care about. I wouldn't recommend it for most people unless you are coming from NixOS, know a lisp dialect, and/or are willing to put in a lot of effort.

Trisquel provides a good experience out of the box imo, as long as your hardware is supported and if you don't mind the dated looking interface. I used it for a while on my corebooted laptop.

I didn't used much any other "100% libre" distros. As much as I wanted to use it, I never managed to have Guix to run on that machine.

[edit:] to answer OP's question, I would use a distro that ships with it.