You don’t necessarily have to remove all of them. You should particularly watch out for the drilling DOF and you can try using cylindrical coordinate system fir the BCs as mentioned in the referenced CalculiX forum thread.
The question to the OP is if the loads have to be the same in both steps. Usually, the first step only introduces preload and includes so-called dead loads such as gravity while buckling step only includes live (operational) loads such as pressure/force. Sometimes, a slightly different approach is used to introduce load imperfections. This thread is a good example: Issues with linear buckling analysis following ASME PTB-2022 example problem