Yes. That said, there is a possibility you will get push-back from your agency. To be in the best legal position, you should be prepared to show that any protests or other free speech activities took place on your own time.
Most federal employees know that the partial government shutdown is in full swing and there is no end in sight. For the most part, there is little federal workers can do but wait and see what happens.
In late August, President Trump announced his plan to freeze the pay of federal civilian employees. Now, in the midst of the partial government shutdown, he has finalized that plan. On Dec. 28, he issued an executive order formalizing the 2019 pay freeze. Federal workers had been slated to receive a nominal 1.9 percent increase in 2019.