Looking online, I think x220 supports both legacy booting and UEFI. This could be a useful resource

First, of course it is completely fine for /home to be on another drive. As long as it is configured in /etc/fstab correctly, almost any configuration of drives and partitions is okay.

Second, your boot issue sounds very strange. Firstly, x220 has a traditional bios boot, right? So you do not need an /EFI partition, and should install grub to the reserved space on the drive for booting (which if you configured MBR for your drive requires no change, if you configured GPT you need to reserve that space). If you have one of the x220s with libreboot (not sure if that exists, but I used to have an x200 with libreboot flashed for the bios), then your grub version might be very out of date, which could cause issues as well.

I love this channel

Nope, a lot of software will try to bundle as much dependencies as needed by default, which makes building from source much easier. Distributions will then “unbundle” them, to keep packages reusing system libraries as much as possible

Ok, just did. Works fine.

apt install build-essential
apt build-dep emacs
wget https://ftp.gnu.org/gnu/emacs/emacs-30.1.tar.xz
tar -xf emacs-30.1.tar.xz
cd emacs-30.1
./configure —prefix=/usr/local
make
make install

Edit: forgot cd

Nah, building from source takes a few minutes unless you are building a web browser.

I understand it completely. However, my point of view is that, even in the case of the Amazon searches, it was easily disableable. I prefer Ubuntu flavors over base Ubuntu, which are run by the community and only do the bare minimum for Canonical to approve them as flavors (like add firefox as a snap). All of that bare minimum work can be easily undone in my opinion. Though, I understand avoiding Canonical when possible.

In my opinion, go with Ubuntu. First, any issues you have with Ubuntu can be fixed easily; snaps can be easily removed, as well as amazon links, gnome tweaks and the rest. Second, unlike Debian, Ubuntu has the hardware enablement stack, which means that any supported Ubuntu release will run on hardware newer than that release, and your graphics card should run with a much newer driver. Any gaming distros built on Ubuntu are probably fine, but will only give marginal improvement to FPS.