Sitefinity 5.4 hotfix came out today, and they have not yet build a new Thunder version against it. It will probably be out tomorrow (Wednesday).
Hello Kevin, We have just released Sitefinity Thunder 184.108.40.206 which includes support for Sitefinity 5.4 hotfix (5.4.4010.0). I apologize for any inconvenience which this delay might have caused you. Please let me know if I can be of further assistance. All the best, Marin Atanasov the Telerik team