how to purge sick old pep Grub in multiboot Ubuntu20.4

[kalpana]

Have a 3 boot side-by-side installation: Win10, which hasn't booted for 3 years (reboot virus on version update), Pep9, which was sick, + also recently stopped booting, and Ubuntu 20.4.5, which got sick when I used the sick Peppermint for a week after 6 months with no problem. Have been running it only on RECOVERY Ubuntu. Just did full Boot-Repair Program from a boot stick, inc fix Windows, purge and reinstall Grubs, but see the Pep9 grub is still there with old Ubuntu20.4 kernels, boot-repair script says it was purged and reloaded. Although the Repair seemed to all work OK, I haven't tried the Windows (or Ubuntu- still on boot stick) yet, wanted to clean any source of infection or problems.

BUT I WANT TO PURGE IT COMPLETELY from the Live Ubuntu stick in Terminal. It IS booting up from the Ubun20.4 Grub Now, after that got sick, it had defaulted back to Pep9 GRUB. Notice those 2 Pep kernels are very fragmented, 4-15.0-196 has 114 pieces. Can I do that without messing up the new Ubun20.4 Grub?? Also wanted to purge + reinstall the last Ubun kernel (an option in Boot-Repair, but didnt check it- it purges ALL of them first). Could I do that ALONE, if I uncheck everything else on Advanced Boot-Repair? Best would be terminal commands to do those 2 things, remembering I'm running it off an identical LIVE UBUNTU stick. I am not a complete imbecile (been using Ubun since 2008), but terminal commands are never explained, and manuals have too few examples to really understand them. The Peppermint (+ then Ubuntu) gave all the signs of viral infection, erratic behavior, programs closing or disappearing suddenly.

On another note, is there anything in Ubuntu 22.4 that doesn't work with my lappy? And what is a very light efficient Ubuntu, seems Peppermint gave up the ghost- newest still based on Ubun18.4?

Dell Inspiron 15-3467? CoreI5, 8gb ram, 2 Tb drive
Thanks for any help.