A card to open a door at a hotel on Shabbat

In my personal opinion, no, but there are poskim who have made it easier (like Rabbi Rabinowitz, z"l, of Ma'ale Adumim. I think he also thinks it should be prohibited in practice because of Ovadin Dachul or something like that). See here: http://www.shut-halacha.co.il/question_print.php?id=5718 See also here a summary of Mikkel by Rabbi Rabinowitz's student, Rabbi Eli Reif: https://www.toraland.org.il/%D7%9E%D7%90%D7%9E%D7%A8%D7%99%D7%9D/%D7%98%D7%9B%D7%A0%D7%95%D7%9C%D7%95%D7%92%D7%99%D7%94-%D7%95%D7%A8%D7%A4%D7%95%D7%90%D7%94/%D7%98%D7%9B%D7%A0%D7%95%D7%9C%D7%95%D7%92%D7%99%D7%94-%D7%95%D7%94%D7%9C%D7%9 B%D7%94/%D7%A9%D7%99%D7%9E%D7%95%D7%A9-%D7%91%D7%93%D7%9C%D7%AA%D7%95%D7%AA-%D7%9E%D7%92%D7%A0%D7%98%D7%99%D7%95%D7%AA -%D7%95%D7%91%D7%9B%D7%A8%D7%98%D7%99%D7%A1-%D7%96%D7%99%D7 %94%D7%95%D7%99-%D7%93%D7%99%D7%92%D7%99%D7%98%D7%9C%D7%99/