"Burnt to disk" rather than put the image on a USB drive (diskkey, thumbdrive or whatever) ?
I usually update using the USB but Ubuntu's own "Startup Disk Creator" is notoriously unreliable when using the next release's ISO. So I use
https://help.ubuntu.com/community/mkusb - its not pretty but works reliably. Might be worth trying.
Anyway, for my main working machines I use Ubuntu Mate LTS, upgrading is a time consuming and somewhat nervous time, the LTS version minimizes that problem. Its pretty rare for me feel I am missing out on anything by not doing the 6month cycles, the very few things can be covered by a PPA with latest release.
I did have problems with the official Ubuntu Lazarus DEBs, perhaps because I expected things like F1 help to work out of the box, not sure. Anyway, using the 1.8rc series, manually installing using the FPC/Lazarus DEBs, no problems (maybe because I'm now happier with the Lazarus approach ?).
For some software testing, I have been using debian Gnome 3 in a VM and it looks good, I'd expect Ubuntu 17.10 would be similar but maybe too demanding of resources on my laptop. I may put 17.10 on the desktop and would expect Lazarus 1.8rc to go on easily. I would not use the Ubuntu packages to install Lazarus.
My experience with Mint dates back to when Ubuntu started shipping Unity. While its probably a lot better now, not everything I needed was quite convinced it was Ubuntu. Mint looked great but I went to Ubuntu Mate for an easy life.
David