I also have had lots of difficulties with constipation since Covid has been around. No issues before. Lots of tests with normal results, lots of trying prescription medications, laxatives, low Fodmap diet. What I've had mine narrowed down to has been SIBO and more specifically IMO (intestinal methanogen overgrowth). Test to figure this out was a TrioSmart breath test and treatment is a course of 2 expensive antibiotics for 2 weeks. But for me this keeps recurring and there is no identified cause.