Where am I likely to find mod_jk.so for apache 2.4.46 ?
I tried to build it, first attempt
./configure --with-apache=/home/pi/Downloads/httpd-2.4.46
You are trying to build a static module.
Why don't you try to build a shared module instead?
./configure --with-apxs=/usr/local/apache/bin/apxs
make
make install