Currently using the latest 18.04 LTS on a variety hardware, I like how it just works with very little need to tweak, as I don’t have time to do that anymore.
I found that installing “/“ onto SSD and moving /var & /tmp to /home (on HDD) just crashed at boot up when done through fstab using binds, when using “ln -s” to link instead applications like cups & Firefox just stopped working.
The best headache free to use both a SSD & HDD, and avoid putting unnecessary wear on the SSD is to just to make the SSD /usr and move /opt to /usr/local/opt then “ln -s /usr/local/opt /opt”. The boot up may not be as fast, but I only boot my system only once a day, so no biggie. I’ve been using the new setup for a week now, and it’s very stable, with the desktop applications loading lightning fast.
As Ubuntu evolves, sometimes the old tricks don’t work anymore, so we have to find new ways to make things work.
(Been using Linux since 2000)