Why do you need a USB stick? If the answer is "I use 10 different computers per week," the web app is faster than finding a USB slot. If the answer is "I have no admin rights to install software," use the web app. If the answer is "I have no internet," DeepL Pro requires internet except for the specific offline model (which won't fit on a standard USB).
“Portable DeepL Pro is a paradox – but these hacks get you 90% there.” deepl pro portable