Akvan said: “In most places aniccha, dukka, anaththa is referred to as the thilakkana, and you refer to it as three marks of existence.”
I have used both “three characteristics of nature” and “three marks of existence” to translate the Pali word Tilakkhana to English. If you look at popular English translations, people have used both those translations.
I also use just Tilakkhana at many places without translating too. That is the best, but one who is not familiar with the Pali word may get stuck. So, I have to use those common English translations too.
Akvan said: “However, in most sutta’s aniccha, dukka, anaththa are referred to as sanna”. and “But can you share any sutta’s that refer to aniccha, dukka, anaththa as lakkana?”
Different suttas have used both those terms. For example, Sabbasava sutta used “anicca sanna“. Anattalakkhana Sutta has “anatta lakkhana” in the title itself.
We should not get hang up on words. As you said:”I know that talking about whether it is a lakkana or a sanna will have no difference to the understanding of aniccha, dukka and anaththa”. That is exactly right. One just need to comprehend what is meant. Understanding is deeper than just description by words. On the other hand we have to use words to convey the idea to others. As long as the idea gets across that is fine.
Key Pali words like anicca and anatta cannot be translated word to word. They could be described in several (related) ways.
This is why my description of anicca or anatta may vary somewhat from post to post. But they are all inter-consistent.