I have a table which has sorting disabled but you can still group (even though the rows get sorted) and it worked fine until one of the recen upgrades. Now the group icon does not show.
Support Forum
Looks like a bug yes, we'll get it fixed! https://github.com/bryntum/support/issues/7128
This still doesn't work after the upgrade to v5.4.1
You can test in https://bryntum.com/products/grid/examples/grouping/ by setting features in the config to this:
features : {
sort : false,
group : true
}