For Ubuntu Studio, I cannot upgrade my kernel version

Question

I need to upgrade my kernel version from 5.15.0-40-lowlatency to latest version which is 5.18.6. I tried a lot of methods. The codes successfully run in the terminal, but after I reboot, it still stays the same kernel version which is 5.15.0-40-lowlatency. These are the code I used (one of the method I tried).

wget https://raw.githubusercontent.com/pimlie/ubuntu-mainline-kernel.sh/master/ubuntu-mainline-kernel.sh
sudo install ubuntu-mainline-kernel.sh /usr/local/bin/
sudo ubuntu-mainline-kernel.sh -c
sudo ubuntu-mainline-kernel.sh -i
sudo reboot
> subaitha@subaitha-virtualbox:~$ wget https://raw.githubusercontent.com/pimlie/ubuntu-mainline-kernel.sh/master/ubuntu-mainline-kernel.sh
--2022-06-29 19:32:26--  https://raw.githubusercontent.com/pimlie/ubuntu-mainline-kernel.sh/master/ubuntu-mainline-kernel.sh
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 185.199.109.133, 185.199.111.133, 185.199.108.133, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|185.199.109.133|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 26474 (26K) [text/plain]
Saving to: ‘ubuntu-mainline-kernel.sh.5’
ubuntu-mainline-kernel. 100%[===============================>]  25.85K  --.-KB/s    in 0.05s

2022-06-29 19:32:27 (477 KB/s) - ‘ubuntu-mainline-kernel.sh.5’ saved [26474/26474]
> subaitha@subaitha-virtualbox:~$ sudo install ubuntu-mainline-kernel.sh /usr/local/bin/[sudo] password for subaitha:
> subaitha@subaitha-virtualbox:~$ sudo ubuntu-mainline-kernel.sh -c
Finding latest version available on kernel.ubuntu.com: v5.18.8
Finding latest installed versiondpkg-query: no packages found matching linux-image-unsigned-5.16.0-051600-generic_5.16.0-051600.202201092355_amd64.deb
: none
A newer kernel version (v5.18.8) is available
> subaitha@subaitha-virtualbox:~$ sudo ubuntu-mainline-kernel.sh -i
dpkg-query: no packages found matching linux-image-unsigned-5.16.0-051600-generic_5.16.0-051600.202201092355_amd64.deb
Finding latest version available on kernel.ubuntu.com
Latest version is: v5.18.8, continue? (y/N) 
Will download 6 files from kernel.ubuntu.com:
Downloading amd64/linux-headers-5.18.8-051808-generic_5.18.8-051808.202206290850_amd64.deb:  0% 100%

Downloading amd64/linux-headers-5.18.8-051808_5.18.8-051808.202206290850_all.deb: 100%

Downloading amd64/linux-image-unsigned-5.18.8-051808-generic_5.18.8-051808.202206290850_amd64.deb: 100%

Downloading amd64/linux-modules-5.18.8-051808-generic_5.18.8-051808.202206290850_amd64.deb:  0% 100%

Downloading amd64/CHECKSUMS: 100%

Downloading amd64/CHECKSUMS.gpg: 100%

Signature of checksum file has been successfully verified
Checksums of deb files have been successfully verified with sha256sum
Installing 4 packages
Cleaning up work folder

.

subaitha@subaitha-virtualbox:~$ sudo update-grub
[sudo] password for subaitha: 
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.15.0-40-lowlatency
Found initrd image: /boot/initrd.img-5.15.0-40-lowlatency
Found linux image: /boot/vmlinuz-5.18.8-051808-generic
Found initrd image: /boot/initrd.img-5.18.8-051808-generic
Found linux image: /boot/vmlinuz-5.18.8-051808-generic
Found initrd image: /boot/initrd.img-5.18.8-051808-generic
Found linux image: /boot/vmlinuz-5.18.0-051800-generic
Found initrd image: /boot/initrd.img-5.18.0-051800-generic
Found linux image: /boot/vmlinuz-5.16.0-051600-generic
Found initrd image: /boot/initrd.img-5.16.0-051600-generic
Found linux image: /boot/vmlinuz-5.15.0-40-lowlatency
Found initrd image: /boot/initrd.img-5.15.0-40-lowlatency
Found linux image: /boot/vmlinuz-5.15.0-40-generic
Found initrd image: /boot/initrd.img-5.15.0-40-generic
Found linux image: /boot/vmlinuz-5.15.0-24-lowlatency
Found initrd image: /boot/initrd.img-5.15.0-24-lowlatency
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.
done
subaitha@subaitha-virtualbox:~$ sudo reboot