Guide about how to update kernels in Qubes OS 4.1. If kernel you want is in qubes-dom0-unstable repository, follow https://www.qubes-os.org/doc/managing-vm-kernels/
Assume AppVM is disp1 and you have qvm-copy-to-dom0 script in dom0.
Select kernels you want from https://ftp.qubes-os.org/repo/yum/r4.1/current/dom0/fc32/rpm/
Make sure have three rpm because some kernels only have kernel-latest-*.qubes.x86_64.rpm.
kernel-latest-*.qubes.x86_64.rpm
kernel-latest-devel-*.qubes.x86_64.rpm
kernel-latest-qubes-vm-*.qubes.x86_64.rpm
Suppose we want to install 5.16.18.
After downloading kernels to Download of disp1, compress them to a single file because qvm-copy-to-dom0 can't copy directory.
In disp1, run:
cd ~/Downloads
tar cvzf 5.16.18.tgz *5.16.18*
In dom0, run
kernel_version=5.6.18
mkdir $kernel_version
cd $kernel_version
qvm-copy-to-dom0 disp1 ~/Downloads/$kernel_version.tgz $kernel_version.tgz
tar -xvf $kernel_version.tgz
sudo dnf install -y kernel-latest-*.qubes.x86_64.rpm
sudo dnf install -y kernel-latest-qubes-vm-*.qubes.x86_64.rpm
# install dependencies of devel
# if you need other dependies, search how to install them in Fedora, and replace `dnf install` with `qubes-dom0-update`
sudo qubes-dom0-update -y elfutils-libelf-devel
sudo dnf install -y kernel-latest-devel-*.qubes.x86_64.rpm
rm -rf ../kernel_version