Unfortunately Lemmy cannot allow to post ASCII art properly

sure it can, you just need to use markdown to make it render in a monospace font (put three backtick characters on the lines before and after; click lemmy’s “view source” button on this post to see what it looks like):

 _ _ _          _   _     _     
| (_) | _____  | |_| |__ (_)___ 
| | | |/ / _ \ | __| '_ \| / __|
| | |   <  __/ | |_| | | | \__ \
|_|_|_|\_\___|  \__|_| |_|_|___/