Multiple values in radio input within form with vanilla HTML
I'm pretty sure this is not posible in modern browsers without the use of JS. Maybe on old browsers you could do some tricks with CSS and display:none because it used to not send fields with display:none, but nowdays that is not an option.
If you can allow Javascript, you can add a data attribute to each radio option and use it to populate an extra hidden input on change.
document.querySelectorAll('input[type=radio][name="someParam"]')
.forEach(radio => radio.addEventListener('change', (event) =>
document.getElementById('someOtherParam').value = event.target.dataset.extraValue
));<form method="GET" action="https://mywebsite.com/somedirectory/">
<input type="radio" id="uid1" name="someParam" value="fruity" data-extra-value="apple" />
<label for="uid1">Fruit</label>
<input type="radio" id="uid2" name="someParam" value="veggie" data-extra-value="pepper" />
<label for="uid2">Vegetable</label>
<input type="hidden" id="someOtherParam" name="someOtherParam">
<input type="submit" value="Submit" />
</form>