Editing my long-winded post…
As a step-above-noob, I’m still a bit apprehensive when working with the command line interface for fear of making a total mess and bricking my laptop, but I was able to sleuth out solutions to these errors for myself this time… with ample time to scour forums and a few deep breaths, haha!
I hope other noobs and not-so-noobs might find this useful, but if not, dear moderators, please feel free to delete!
After a failed attempt to get ProtonVPN running in amber (which involved ProtonVPN support and a slew of uninstalls, reinstalls, purges, cleans, autoremoves, updates and upgrades), I was derailed by a couple of errors…
lzma_read: Read error (7) E: Some index files failed to download. They have been ignored, or old ones used instead. E: Splitting of clearsigned file /var/lib/apt/lists/repo.puri.sm_pureos_dists_amber_InRelease failed as it doesn't contain all expected parts E: The package lists or status file could not be parsed or opened.
and
Reading package lists... Error! E: Splitting of clearsigned file /var/lib/apt/lists/repo.puri.sm_pureos_dists_amber_InRelease failed as it doesn't contain all expected parts E: The package lists or status file could not be parsed or opened.
And when I tried to launch Software via Show Applications, I got this similar head-scratching message:
As per advice elsewhere — here and here and here (because a second and third opinion are always good!) — I ran sudo rm /var/lib/apt/lists/* and sudo apt-get update. That seemed to remedy the two errors. Then, I ran ‘sudo apt upgrade’ and was back to smooth sailing!
Thanks to those who’ve advised in the past. Your technical and moral support really helped. 