The current version of `memtest86+` (v5) on all currently-supported Ubuntu versions cannot handle running under UEFI, which means that the option to run it doesn't appear in the GRUB boot menu when Ubuntu is installed or when booting from an Ubuntu live USB drive on those modern computers that have legacy BIOS mode disabled, which is somewhat common.
I'll prepare the backports to Jammy if backports team will accept it: +source/memtest86+/+bug/1998834
If you need check ram of computers where is not present legacy bios option you can do a cd or usb drive with the iso in the package (/usr/lib/memtest86+/memtest86+x64.iso) from 6.00 package.
I also used the iso of 5.31b from debian experimental since I started to works on it one year ago because 5.01 in debian/ubuntu live was not working on major of system.
6.00 had a major code rewrite and is "recent", I suppose is not possible will be migrate to stable (and probably need more tests and fixes before) and add in live iso (of LTS already released and still supported), and there is also no secure boot support for now:
Red Hat Enterprise Linux ships a memory test tool called memtest86+. It is a bootable utility that tests physical memory by writing various patterns to it and reading them back. Since memtest86+ runs directly off the hardware it does not require any operating system support for execution.
To boot memtest86+ from the rescue disk, you will need to boot your system from CD 1 of the Red Hat Enterprise Linux installation media, and type the following at the boot prompt (before the Linux kernel is started):
If interested in having it in RHEL, please open a support case asking to have v.6 of memtest86+ included in the distro: it may be included in RHEL9, since is still in the Full Support phase of its lifecycle.
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