Can't boot Ventoy for Xubuntu on brand new HP

[MR ZenWiz]

I bought a new HP laptop for my partner so we could upgrade her main
machine (and we could cycle through the others to get rid of the
oldest, now broken HP laptop).

I got it at Costco for a great price.  However, it is ungodly slow (in
large part I suspect due to its internal 5400RPM hard drive, partly
from its i5 processor).

I figured I'd just replace the hard drive with her previous 1TB SSD -
piece of cake, right?  I've been doing this sort of thing for almost
40 years now.

Not a chance.

Issue #1: I cannot get the bloody thing open.  I downloaded the
service manual, and it says to undo all the screws (duh) and use a
plastic tool to pry open the lid (I have such a tool).  Only there is
absolutely no place where there is room to insert the pry tool and
nothing on which to gain leverage to pry it open.

This may be a good thing because of issue #2: I put Xubuntu 20.04 (and
a few others) on a Ventoy USB drive and the HP refuses to boot it.  It
says:

Secure Boot Violation
Invalid signature detected. Check Secure Boot Policy in Setup.

1. This is exactly the same USB flash drive I used to reinstall
Xubuntu 20.04 in her old Dell with a new-ish SSD I installed (WAY
easier installation with the manual, to Dell's credit).  It has the
UEFI config setup on the flash drive - the Dell also has secure boot
enabled in UEFI. This works perfectly.

2. Does anyone know if there is some new UEFI signature process since
Ventoy 1.0.61?

I looked around on the web and found mention of a possible fix using
balenaEtcher to put an image of Super-UEFIinSecureBoot-Disk.img on the
drive, and it still won't boot - the MOKMANAGER piece on the drive
gets the same error.

I tried to disable the secure boot in the BIOS, but it's so picky
about that that it requires numerous steps that, frankly, are too much
of a pain for such a slow operation, especially when I can't even get
the thing open to replace the drive.  I was thinking about paying
someone to do that, but there's the issue with the warranty (duh).

1. Is there some kind of new UEFI signature process that Ventoy
doesn't know about?  I see there's a 1.0.62 version, but the notes
don't say anything about this.

2. Is it a better option to return the bloody machine and get a new
Lenovo?  I found one that might do nicely (doesn't have full HD, but
whatever) assuming I can get the thing open to install my SSD (that
already has Xubuntu 20.04 installed and was working).

All (positive) feedback welcome.

Thanks to all.

Mark Richter, Lead Software Engineer
Award-winning Author, "Mystic Prince" (on Amazon)
Avid Xubuntu user/admin/fan
http://www.linkedin.com/in/markrichter1
Registered Linux User #472807 http://counter.li.org/
FSF Member #12694 http://www.fsf.org