How to make fish treat question mark and ampersand as normal characters

set -U fish_features qmark-noglob

Then logout and log back in.

To get the simpler ampersand, you have to compile fish 3.4:

cd ~/forks/fish-shell
make -j4
sudo make install

then the feature is:

ampersand-nobg-in-token

Strangely this doesn't seem to work without running the shell from the built location.

When it works it looks like:

fish-shell $ echo a&b?
a&b?