A little late to the party but I dug out my V5 tablet and wanted to see what happens if I'll do everything from the scratch.

Long story short, no surprises for as long as 3.3.0.16.
3.4.0.24 installs but boots in blank screen (as somewhat expected). Wifi worked though, so I could SSH in (still 'nemo', not 'defaultuser') and install SFOS4 (4.0.1.8)—again blank screen.

SSH worked still so I tried re-installing the compatibility packages There were some errors but some of it seemed to install. Alas, rebooted back to blank screen so I'm taking a wild guess this has something to do with the screen/gfx driver

Maybe the next thing could be re-installing to 3.3.0.16, take a dmesg, install 3.4.0.24 and compare a dmesg from that to the previous one, but that's about all I can think of. (When is another thing)

Almost forgot, droid-system-tbj is possibly a Jolla C package, see here.

At some point I installed Alien Dalvik from The Jolla Store but it made no difference later when trying to install the droid-compat-v820w packages. Then again, the droid-system-tbj necessarily doesn't even matter, see this.

EDIT: dmesg for 3.3.0.16 & 3.4.0.24 included

EDIT2: Thought I'd see how far I can update via SSH:

• 4.0.1.48 boots to blank screen like before.
• 4.1.0.24 installs but the tablet never goes past the ANDROID text at reboot.
  If anybody asked me, I'd say there's no point going past 3.3.0.16 with a V5 tablet unless somebody figures a way to fix the blank screen and even then anything past 4.0.1.48 is uncertain (but at least it would be SFOS4)