Instrument flashers out
The turn signals get their power from the turn signal flasher and with them working front and rear on your exterior lights , switch should be good.
You should find on your schematic with your shop manual the power from the turn signal switch should split off from the turn signal outputs , usually the front ,to the instrument panel.
If the feed is good at the cluster connector , then check the bulbs and circuit board ground and power feeds on the instrument cluster,or a bad connector.
Should be able to use an ohm meter to check the printed circuit on the instrument cluster while its out and the bulb filaments for continuity.