Abstracting from the fact that it is usually pronounced as in English, how /etc (https://www.tldp.org/LDP/sag/html/etc-fs.html) should be pronounced in Russian? I was under the impression that, as it transliterates to /етц, it should be pronounced as "ye te tse". That is the way Mr. Дмитрий Молчанов pronounced it in "Администрирование Linux. Лекция 4" (https://www.youtube.com/watch?v=_dFxopSVe5Y) at around 18:16 and Mr. Anton Pavlenko in "Структура каталогов Linux и монтирование дисков. Как продлить жизнь SSD." (https://www.youtube.com/watch?v=j7iKs5xiujM) at around 10:45.
However, according to my Russian colleagues, also IT specialists, it transliterates to /этц and should be pronounced as "e te tse".