I have installed Ubuntu 20.04 at another partition than where a previous Ubuntu 18.04 has installed. But failed to boot, and systemd seems are waiting for the swap partition to be mount. So I just comment the swap line out from fstab file. But it still hangs, so I chrooted into it and run
systemctl mask dev-nvme0n1p8.device
And reboot.(nvme0n1p8 is the swap) It still hangs on systemd-rfkill.sevice and journal shows it always timeout. But after I deleted the swap partition, it can boot now without any problem.
Btw, the 18.04 is always usable. Screenshot when booting
Update on 20th May:
My laptop is Samsung Notebook 9 pro NP940X5N with i5-8250U. After I deleted the swap partition, this bug still exists. And I found another post about it: Mostly unable to boot when [ ***] A start job is running for... FOREVER! It seems that there is still a rare probability to boot normally, and it exactly happened after I deleted the swap partition. And I tried more time later. if I turned off my laptop for a long time, on the next boot, it may more probably boot. but it mostly just doesn't work.
