I am running Debian testing with kernel 5.10.0-6-amd64, xserver-xorg-video-amdgpu and firmware-amd-graphics from the Debian repo. Probably the same with the Ubuntu repo. The latest kernel I think you can use with amdgpu-pro-21.10-1247438-ubuntu is the one used by ubuntu 20.04 or 20.10. The kernel used by 21.04 is not supported yet afaik.
For Debian I only needed the driver for OpenCL (for mining) and installed it with the following command, Ubuntu hirsute should be the same:
amdgpu-install --opencl=legacy --headless --no-dkms
If you are using Vega or higher you can try
amdgpu-install --opencl=legacy,rocr --headless --no-dkms
cheers