EXT:powermail
Friendly Captcha can be used in EXT:powermail by following these steps:
Setup
TypoScript and Page TsConfig need to be extended.
Add TypoScript
Either import the TypoScript manually in your site package or add the following line to your TypoScript template:
@import 'EXT:friendlycaptcha_official/Configuration/TypoScript/Powermail/setup.typoscript'
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or select the TypoScript in your TypoScript record

Add TypoScript
Add Page TsConfig
Either import the TsConfig manually in your site package or add the following line to your TsConfig files :
@import 'EXT:friendlycaptcha_official/Configuration/PageTsConfig/powermail.typoscript'
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or select the TypoScript in your TypoScript record

Add Page TsConfig
Usage
It is now possible to select Friendly Captcha as a field type in a powermail field record

Add Friendly Captcha to your form
Result
The result should look like this:

Result