This is sort of second-hand advice, because luckily I’ve never really had any kind of skin/hair issues (except that I’m now losing the later, but I made peace with that and shaved my head)
But my wife has had some dandruff issues in the past, so I’ve learned a little from her.
Part of the issue is that there’s kind of several different issues at play that cause dandruff or dandruff-like symptoms, and common usage of the term often doesn’t really differentiate between them very well, even though the appropriate treatments for them may be very different.
For a long time, a lot of focus with dandruff was on fungal causes, and so a lot of the commonly-available anti-dandruff shampoos and treatments work, at least in part, by being antifungal.
Of course, if your dandruff isn’t actually caused by fungus, antifungal ingredients won’t do anything to help with your dandruff problem, and may even make it worse by drying out or irritating your scalp. That turned out to be my wife’s case, and her issue improved significantly by basically switching to any other shampoo besides anti-dandruff. It took a little fine-tuning and trial and error to figure out which shampoo and conditioner worked best for her, but the big first step was staying away from anti dandruff products.
There’s a lot of different combinations of hair types, skin type, and underlying conditions that could be at play, so there’s no-one-size-fits-all solution. If you haven’t already, a good first step is probably to talk to a dermatologist, or if you already are working with one, it may be time to look for a new one.
Failing that, do some research, figure out what send like is most likely to be causing your issue and the l how to treat it, try some things, if they don’t work, try some different things, repeat as necessary.