Bevelled text cutout

Good evening

Someone has an idea how to cut out a bevelled letter or text from a cube?

I can bevel a letter fine with the supplied modifier after adding a depth and convert it to mesh:

But when using this letter as boolean difference modifier on a cube, I get a weird mesh:

When converting the letter with applied depth to a mesh first and add a bevel modifier, the letter isn’t bevelled at all:

Is there any other way to have clean bevelled letter cut out?

thanks in advance

Without cleanup that’s just not possible. It will create concave ngons that don’t bevel well, or do anything else well for that matter.
Convert just the base letter, without extrusion or bevel. After converting, limited dissolve it and remove doubles (increase merge distance a little bit), then cut it up into convex ngons. Add a Solidify and Bevel modifiers, clean up the remaining areas where there’s still overlap. Setting Outer Miter to Arc in Bevel modifier might help.
However, when you do do the cutout, you’ll get the same problem on the cube, and will need to clean that up as well.

Not sure if it suits your needs, but have you seen the engraver add-on?