Hi, this kind of hijack can be caused by an add-on.
Question: when you are typing in the address bar, does the top line of the drop-down already show that the search will be diverted to Bing, or does it mention your preferred search engine and then it gets diverted after you submit the search?
I suggest posting this problem on the Mozilla Support site. They have a team of support volunteers to troubleshoot malfunctions with your currently installed version of Firefox, while this site is focused on idea submissions for future versions of Firefox (looking ahead anywhere from 8 weeks to many months). Here's a link to the new question form (for Windows/Mac/Linux): https://mzl.la/3y1vQUQ
