@filip Great work on the installer
Keep it up
The "resume device" hang propagated to Stretch as well. And for once it actually has nothing to do with systemd.
You were right, issue was introduced in "initramfs-tools", v128 in order to fix the bug where some NVMe drives were slow to enumerate partitions causing the system to fail to resume from hibernation...
and a bug report.
The weird part is the wait time they've set ( ~20sec ). I mean what for, seriously!? Even the guy who reported the bug said that adding a 1sec delay fixed the issue for him...
Anyway, until they sort it out, the quick fix is to add the "resume=/dev/sdXY" to the "GRUB_CMDLINE_LINUX_DEFAULT" in "/etc/default/grub" file, where "/dev/sdXY" is your swap partition ( worked for me atleast @Stretch ).
You might even get away with any partition ( not just swap ), as long as you don't have any data on it ( untested!!! ).
I've also looked at the actuall shell scripts used, however I'm having a bit of a hard time reading them ( I've never really understood why Debianers always write shell scripts in such obfuscated and "hard to read" way
I'll let you know If I get anywhere with that...