How can my breadmaker made wholemeal bread taste less salty?
Salt is an important part of the baking process, as your breadmaker instructions will probably state.  Most/All bread makers will come with Recipes and probably tips or guidance on baking.
I did experiment with low salt recipes, but have not kept my notes on that. From memory I had the best results with about half the standard amount of salt, but usually disappointing results if I tried to go salt free. Basically the salt tends to inhibit the yeast, so if you just reduce the salt content the uninhibited yeast activity causes it to over-rise, and then collapse to result in a loaf with a convex instead of concave top.
You need to counteract this by reducing the amount of yeast, or otherwise juggling with the recipe. Also consider the amount of sugar and the initial temperature of the ingredients to get consistent results it is best to watch all of these factors and record your results.  Also  note what oil/fat/butter is used and whether if butter it is salted or unsalted.
Here are some internet links I found

Davids Blog  Salt-Free Breadmaker Bread. That has a wholemeal and a brown bread recipe both with no added salt.
http://www.bloodpressureuk.org/BloodPressureandyou/Yourlifestyle/Eatingwell/Yourfood/Salt-freebread another set of recipes, including wholemeal bread with no salt and suitable for a breadmaker machine.
This one is more of an explanation and discussion of the purpose of salt in bread-making https://www.weekendbakery.com/posts/salt-in-bread-baking-how-much-and-why/ Note in the UK there are recommendations to reduce salt content.
https://breadmachinerecipe.net/low-salt-bread-machine-recipe/  although I wonder if the yeast quantities should be teaspoons not tablespoons