For trans people it depends.

If you're just starting estrogen-oriented HRT and you're at a weight considered ideal for your pre-HRT body, then it is helpful to actually gain a few kg of fat, together with weekly hours of intense activity (like running, bicycling, squatting and planks, hip thrusts) coupled with moderate activity (like walking half an hour everyday) Then fat redistribution will be more effectively towards a )( body shape, with breast growth improved. This guide may help.

For testosterone-oriented HRT, I'm less certain, though I assume the fat redistribution's accent is more on weight loss and exercise for muscle growth. Lifting, bench presses, planking, and the like for \/ bodies. Here's a good training scheme.

That said, everyone has their own goals; important is that one remains healthy. A good diet is balanced and lowly processed.

A body fat percent healthy for all people (binary and nonbinary) would be around 14-25%. If you can get pregnant (and seek to do so), it's better to be a little higher in this range, because during pregnancy, your body will prioritise the embryonic/fetal needs more than yours.