Man page search – how can I turn off the highlighting after matches found

You can use Alt+u to remove the highlight on last search results.
You can highlight them again with Alt+u, it's a toggle.

Switching off the highlight does not switch off the status column, showing marks on each line containing a match, if the column is enabled using options -J or --status-column or keys -J.

To hide the status column, use -+J.

To show the status column, use -J.

(Technically, Alt+u it's equivalent to ESCu on terminal level - that is why the Alt-key is not mentioned in the man page.)

Actually it uses whatever is specified in the MANPAGER or the PAGER environment variable.

Depending on your man implementation and version there could be also a command line switch to specify the pager.

With the man-db implementation I use all the below ways work:

MANPAGER=cat man man

PAGER=cat man man

MANOPT='-P cat' man man

man -P cat man

To set it permanently, just add it to your ~/.bashrc (or other initialization file used by your shell):

export MANPAGER=cat

That works with some older man implementations too, while MANOPT is man-db specific:

export MANOPT='-P cat'

(Better do not set PAGER that way. That one is used by many other applications too.)

There could be also a global configuration file. man-db has /etc/man_db.conf or /etc/manpath.config. There you can set:

DEFINE    pager    cat

But unfortunately that is taken in consideration only if neither MANPAGER nor PAGER is set.