On Fri, 28 Jan 2022, Eli Zaretskii wrote:

>> Date: Thu, 27 Jan 2022 22:36:39 +0000 (UTC)
>> From: Van Ly <van.ly@sdf.org>
>>
>> When completion-styles is
>>
>>> (basic partial-completion emacs22)
>>
>> # steps to reproduce behavior
>> * start by 'emacs -Q'
>> * customize 'icompletion-vertical-mode' to enable for session
>> * type 'M-x man RET awk'
>>
>> # observed behavior
>> # minibuffer at 'Manual entry:' prompt
>> * shows 'a' of awk and is unresponsive, then 'awk [No matches]' shows
>> * awk RET shows *Man awk* AWK(1) page
>>

>
> I cannot reproduce this: it works for me as expected.  Are you sure
> "M-x man" on your system is capable of completion in the default
> completion mode in "emacs -Q"?  If not, maybe your man-db database is
> missing or outdated?
>

On NetBSD the output from apropos is different in format to the one 
on GNU/Linux.  Could that be why the behavior is stuck?

My system runs "emacs -Q" and the following "M-x man RET a TAB" also 
gets stuck, and this is without attempting to set 
icomplete-vertical-mode.

On GNU/Linux, I observe the expected behavior you see.

On NetBSD, the system release is 9.2 and up to date to pkgsrc-2021Q4.

-- 
vl