I found this font ("Action Man Font") and I would like to use it on the cover of a physical book that I intend to sell.

The license says this:
"
By downloading this font package you agree to the following terms
of use:

- This FONT PACKAGE is FREEWARE and may be distributed ONLY via the
Internet for FREE. Under NO circumstances may this FONT PACKAGE
be sold for a profit nor be included as part of another product or
CD-ROM compilation. If you wish to include this FONT PACKAGE for
FREE distribution on your Web Site, please include all of the fonts
and original documentation supplied with this FONT PACKAGE.

- You may install and use this FONT PACKAGE on an unlimited
amount of machines.

- You may NOT rename, edit, or create any alternate variations of
the fonts included in this FONT PACKAGE.

- This FONT PACKAGE comes "as is" with NO warranty whatsoever.
SHYFONTS accepts NO responsibility for any damages or loss of
any kind due to the use of this FONT PACKAGE. The use of this
FONT PACKAGE is solely your responsibility -- you use this FONT
PACKAGE at your own risk.

Thank you for downloading this font package and enjoy!
"

But it is not clear to me that it can be used for free.

Could someone clarify for me how I can know if the source is for commercial use for physical books and ebooks?
Can those that are for use in ebooks also be used in physical books?

Thank you

Contact the font creator(s). No one else can speak for them. In this case, it could be either Iconian fonts, or Shyfonts.

https://www.iconian.com/commercial.html
https://www.shyfoundry.com/licensing