[Karellen]

I refer to IMDB, because the scraper (despite its name) has the good idea to recognize the files named with their IMDB Id.

You should not be relying on IMDB so much. The scrapers do not use IMDB, they use TMDB. THERE ARE DIFFERENCES BETWEEN THE TWO SITES. I have seen it time, and time again, where people keep referring to IMDB, and TMDB has a different listing.
From now on, when it comes to scraping, ONLY LOOK AT TMDB.
The only reason IMDB works is because TMDB has an IMDB ID recorderd. BUT THEY ARE NOT ALWAYS RECORDED, so you will find that sometimes it fails.

Then maybe I could name my file with its TMDB Id

No

The only problem is that I don't know where it is ?

It is in the URL. The URL also tells you what it is - \movie\ or \tvshow\

Or name it as TMDB, for example Chez Maupassant Season 1 Episode 1 (xxxx) (Where 'xxxx' is the release year) ?

No
You cannot scrape individual episodes on their own.
Episodes are scraped through the tv show. The only thing that matters in the episode file name is S01E01. Everything else is ignored.
If you have named your tv show correctly, and your episodes have the correct S01E01 data in the filename, it will scrape.

I don't understand how the Search engine of TMDB works ; if I search for "Most Dangerous Game (2020)" - there is nothing in return. But if I type "Most Dangerous Game" .. it's found as "Most Dangerous Game (2020)"

When you search in the TMDB website, don't add the year.
When you are scraping, add the year.
Why? I have no idea, ask TMDB why they designed it that way.

Well anyway thank you for your answer, I understand that TMDB returns only the "movies".

Why does TMDB only return movies?

My last bit of advice... Stop referring to IMDB.
If you keep doing that, you are just going to continue being confused.