WPF command /w boolean parameter leaves button disabeld

Question

I'm having an issue with binding a Command to a button, with a Boolean CommandParameter. The result is always a disabled/not clickable button.

In WPF with the relayCommand from Microsoft.Toolkit.Mvvm. https://learn.microsoft.com/en-us/dotnet/api/microsoft.toolkit.mvvm.input.RelayCommand

the code: XAML:

...
xmlns:s="clr-namespace:System;assembly=mscorlib"
...
<s:Boolean x:Key="TrueValue">True</s:Boolean>
...

<Button       
    Content="Bool cmd"
    Command="{Binding BoolCommand}"
    CommandParameter="{StaticResource TrueValue}">
    <!--CommandParameter="{Binding SomeBoolProperty}">-->
    <!--<Button.CommandParameter>
        <s:Boolean>
            False
        </s:Boolean>
    </Button.CommandParameter>-->
</Button>

<Button       
    Content="String cmd"
    Command="{Binding StringCommand}"
    CommandParameter="Test"/>

Behind:

    private bool _someBoolProperty;
    public bool SomeBoolProperty
    {
        get => _someBoolProperty;
        set => SetProperty(ref _someBoolProperty, value);
    }

    private ICommand _boolCommand;
    public ICommand BoolCommand { get => _boolCommand ?? (_boolCommand = new RelayCommand<bool>(SetBool, (bool x) => canExecute)); }

    private void SetBool(bool state)
    {
        //...
    }

    private bool canExecute {
        get => true;
    }

    private ICommand _stringCommand;
    public ICommand StringCommand { get => _stringCommand ?? (_stringCommand = new RelayCommand<string>(SetString)); }

    private void SetString(string state)
    {
        //...
    }

Some extra info:

• the xaml is inside a UserControl inside a DataTemplate.
• breakpoint in the SetString function is hit, and has no issues.
• canExecute is not hit.
• 'Xaml Binding failures ' window shows no issues with this.

i did read and try (see the commended code) some variations of this answer: Boolean CommandParameter in XAML

But the button is always grayed out; disabled; not clickable. Any ideas on what causes this button to be disabled?