Hi all, 
thanks a lot to all of you for your splendid input. I´m so pleased. 
@Akito:
In theory it´s really a great suggestion to use CAINE.
That´s secure indeed and would suit my needs (or anybody´s needs for that matter) perfectly. 
Plus: it´s really reassuring that …
The only “negative” point (to me at least) is the size of the download.
Distribution Release: CAINE 11.0 (DistroWatch.com News) mentions its size and apparently it´s 4,138MB! That´s quite hefty. But only for me (I think) as I have to make do with 4.5 GB per month.
Although AldiTalk has changed its policy now and I´ll be able to reign over 5 GB per month next time. 
Nevertheless thanks so much for you suggestion.
Many greetings from Rosika 
@Pranav:
Thanks for your views on the matter as well.
That´s an interesting approach.
If I were to do that the only thing left do achieve is prevent the system (Lubuntu 20.04.2) from
automatically mounting the attached USB stick.
I just found out that PCManFM-Qt (which is my default file manager) has an interesting option under “settings”:
Datenträger: Wechseldatenträger automatisch beim Einlegen einbinden
rough translation:
Disk: automatically embed (i.e. “mount” a removable disk when you insert)
So basically I´d have to uncheck this option. Seems cool.
Thanks so much for your help Pranav.

@berninghausen:
Hi Bill,
Yes, that should be do-able. I have BodhiLinux available as a VM using KVM/qemu/virt-manager.
I´ll probably go for that.
Thanks a lot.
Greetings from Rosika 
@callpaul.eu:
Hi Paul, 
thanks for the stackexchange link. I´ve read it through and it seems quite interesting.
Greettings from Rosika 
@Andy2:
Hi Andy, 
so good to see you here again.
Also a very good suggestion. And perhaps more practical for my purposes as the download size (according to DistroWatch.com: Tails ) is 1.1 - 1.2 GB.
That woud give me the possibility to save up and in the end I could download the ISO. 
Good to know. Thanks for the info. 
Thanks a lot for the compliment. 
I´ll try to stay safe.
@all:
just a bit of a background as far as my original question is concerned:
In the introduction I used the phrase “hypothetical question”, which is true for one part.
But there´s also the real background of the two verbatim USB-sticks I recently ordered from amazon: Verbatim Store ‘n’ Go V3 USB-Stick - 64 GB.
They should´ve been delivered by a certain date but for some undeclared reason amazon couldn´t make it in time and consequently I received an e-mail telling me that delivery would be delayed.
When I finally received the sticks I was wondering about the sending address which was “Amazon Rücksendezentrum” (i.e. something like “Amazon Return Center”) instead of
“Amazon EU SARL”.
I strongly suspect that the sticks were delivered to a wrong location in the first place (hence the delay) and afterwards returned to the “Return Center”. It seems I then got them from there.
Well, I was a bit suspicious at first but when I opened the package I saw the sticks were still in their intact original package.
It may well be I´ve been a bit too paranoid.

Thanks to all of you for your help. 
Many greetings.
Rosika 