I have recently attempted 2 installs from the 19.04 live image/dvd. Both have failed in performing custom partitioning on a drive with another OS on it.
It appeared to have nothing to do with the other OS being there. For example; I select unused space on the (new 1TB w/GPT layout) drive, select create. Am presented with the default type of BOOT, I choose size 200Mb, and mount point none, then OK. After which, it shows the 200Mb BOOT partition, but the remaining (735Gb) space is NOT shown. So it is not possible to create (at least) the root, and swap partitions.
I gave up, and bounced the box to try again. Second attempt was the same experience. So I took the chance of selecting AUTO. Examined the results, which looked reasonable, and said OK. It moved on to Admin/User creation and then began the install. But while the activity in the dialog was moving along as one would expect. There was no disk drive activity. So I performed a CRTL+ALT+F1, and discovered it was complaining about "error no room left on device". Err, what?! This is a C2D@2.5GHz w/4GB RAM, and a 1TB SATA disk. What gives?
Well I performed a ^C in that window to terminate the failed script(s). Then a CTRL+ALT+F2, logged in as root, and issued a halt -p.
Started the system, where I was greeted with a (GhostBSD) mount root problem. Which is another problem of it's own. As this system already has a EFI partition at the beginning of the drive where the new GhostBSD install would have been detected, and listed as an optional bootable system (assuming it had installed correctly).
My problem here is that none of these issues were located in the change log(s) for this release. In fact, it was indicated that this issue was in 18.xx, and had been addressed in this release -- I beg to differ.

I might also note, that this is apparently not a *BSD issue, as I was able to install both the current version of MidnightBSD, and FreeBSD 12.xx without th(is|ese) problem(s).
These issues are IMHO pretty serious, and should be (conspicuously) noted in the install, and release notes/entries.
Any recommendations sincerely appreciated!
P.S. I was (at least) able to fix the EFI partition.
Thanks again.
--Chris