Your understanding is mostly correct for a lot of the industrial unions. There are some attempts by the AfD to get reactionaries into Betriebsrat positions (basically labor representatives in a businesses' management, idk the English term), but they are usually pushed back and unions in Germany tend to have a fairly solid anti-fascist positioning. There are union members who are understandably disillusioned with the SPD, but there are little electoralist alternatives with the Left party currently being busy with a patsoc faction finally splitting off after years and years of infighting, pointless struggle sessions etc. It's kinda dire, honestly. Germany just doesn't have a strong left opposition atm.