Can’t use man command on iSH
iSH doesn’t come with many binaries. You need to install ‘man’ and curl yourself.

apk add man curl


~# man                                                                                                                                                                                                 
-ash: man: not found                                                                                                                                                                                        
~# apk add man                                                                                                                                                                                         
fetch http://dl-cdn.alpinelinux.org/alpine/v3.9/main/x86/APKINDEX.tar.gz                                                                                                                                    
fetch http://dl-cdn.alpinelinux.org/alpine/v3.9/community/x86/APKINDEX.tar.gz                                                                                                                               
(1/2) Installing mdocml (1.14.3-r0)                                                                                                                                                                         
(2/2) Installing man (1.14.3-r0)                                                                                                                                                                            
Executing busybox-1.29.3-r10.trigger                                                                                                                                                                        
OK: 168 MiB in 87 packages                                                                                                                                                                                  
~# man                                                                                                                                                                                                 
usage: man [-acfhklw] [-C file] [-M path] [-m path] [-S subsection]                                                                                                                                         
           [[-s] section] name ...                                                                                                                                                                          
~#