I have this issue too:
[2025-03-18 18:23:25] glpiphplog.WARNING: *** PHP User Warning (512): Error while loading plugin example: Undefined constant Glpi\Plugin\Hooks::ADD_CSS_ANONYMOUS_PAGE in /home/joaco/glpi_10_17/src/Plugin.php at line 355
Backtrace :
src/Plugin.php:355 trigger_error()
src/Plugin.php:950 Plugin::load()
: Plugin->install()
src/Marketplace/Controller.php:546 call_user_func()
src/Marketplace/Controller.php:436 Glpi\Marketplace\Controller->setPluginState()
ajax/marketplace.php:83 Glpi\Marketplace\Controller->installPlugin()

I confirm the issue, on a fresh instance of GLPI 10.0.18 I can't install this plugin.

I called get_included_files() in the "install" method of "src/Plugin.php", and the hooks file of the plugin is not present in the included files :

Array
(
[...]
    [242] => /var/www/glpi/plugins/example/setup.php
    [243] => /var/www/glpi/plugins/example/src/DeviceCamera.php
    [244] => /var/www/glpi/plugins/example/src/Example.php
    [245] => /var/www/glpi/src/Link.php
    [246] => /var/www/glpi/vendor/monolog/monolog/src/Monolog/DateTimeImmutable.php
)

The plugin can't be installed because of those three lines in setup.php of the plugin 'example' :

$PLUGIN_HOOKS[Hooks::PRE_ITIL_INFO_SECTION]['example']    = [ItemForm::class, 'preSection'];
$PLUGIN_HOOKS[Hooks::POST_ITIL_INFO_SECTION]['example']   = [ItemForm::class, 'postSection'];
$PLUGIN_HOOKS[Hooks::SET_ITEM_IMPACT_ICON]['example'] = 'plugin_example_set_impact_icon';

If you comment them you can install the plugin, they were added for the version 11 of GLPI.

Well, there are several distinct issues here.

Original one: Undefined constant Glpi\Plugin\Hooks::ADD_CSS_ANONYMOUS_PAGE is fixed updating to latest GLPI release.

*ITIL* hooks have been introduced in #62 - they exists only for GLPI v11
SET_ITEM_IMPACT_ICON has been added in #55 and also exists for GLPI v11.

You can remove calls as a workaround. I guess those should have been merged in a specific development branch instead of main, or should have been conditionned. Ping @stonebuzz @cedric-anne