[horde] Install as non-privileged user?

[Frank Lienhard]

since I have quite some trouble with my horde installation due to a
server move from centOS6 to centOS7, I'm about to install it anew.

I am using a shared hosting (uberspace), which gives me shell access as
a user.
They also provide php (7.2, 7.3., 7.4.) and pear in the following paths,
which I can access ro:
php: /usr/bin/php
php-pear: /opt/remi/php74/root/bin/

So the question is how do I install this properly inside my doc-root
without any need to install anything in the ro paths?

e.g. I got an error for "horde_lz4.so", because it san't be installed in
the above mentioned pear path.