On these pages:
https://www.percona.com/doc/percona-server/LATEST/installation/apt_repo.html
https://www.percona.com/doc/percona-server/5.7/installation/apt_repo.html

There are two very minor typos in the command to install one of the UDFs:

Should be:

In other words, you have an 'l' instead of a '1' in the function name and in the corresponding so-name.

The same commands, but without the typos, are shown on this page:
https://www.percona.com/doc/percona-server/8.0/management/udf_percona_toolkit.html