I've installed Ubuntu 18.04 (single boot) on a trusty old Dell Latitude E6400. It works very well, but before the Ubuntu Splash screen, right after BIOS boot, a purple screen starts and stays for several (about 20) seconds (as if it was a screen to choose what OS to boot, but this is blank purple), and then the splash screen appears and quickly the login screen. I type the password and a purple screen again which hangs for two or three seconds and then I use the system normally (at least so I think, because my use is very light, really); is all that normal?
I remember I had Ubuntu 16.04 dual boot with MSW7 on a desktop with a basic similar configuration to the Dell laptop and after choosing Ubuntu would go to splash, quickly booting.
Sorry, should've put more information.
systemd-analyze critical-chain
graphical.target @43.688s
└─multi-user.target @43.688s
└─kerneloops.service @36.825s +15ms
└─network-online.target @36.822s
└─NetworkManager-wait-online.service @30.287s +6.534s
└─NetworkManager.service @26.812s +3.472s
└─dbus.service @26.509s
└─basic.target @26.472s
└─sockets.target @26.472s
└─snapd.socket @26.435s +35ms
└─sysinit.target @26.418s
└─cryptsetup.target @26.418s
└─systemd-ask-password-wall.path @3.936s
└─-.mount @3.859s
└─system.slice @3.886s
└─-.slice @3.859s
systemd-analyze blame
22.416s dev-sda1.device
21.133s systemd-journal-flush.service
14.562s systemd-sysctl.service
14.209s keyboard-setup.service
13.383s plymouth-quit-wait.service
13.044s systemd-udevd.service
10.576s fwupd.service
6.534s NetworkManager-wait-online.service
6.212s plymouth-start.service
5.086s snapd.service
4.514s apparmor.service
3.472s NetworkManager.service
3.468s apt-daily-upgrade.service
3.271s udisks2.service
3.045s systemd-tmpfiles-setup-dev.service
2.589s accounts-daemon.service
2.535s ModemManager.service
2.350s thermald.service
2.007s networkd-dispatcher.service
1.818s snap-gnome\x2dcharacters-117.mount
1.817s plymouth-read-write.service
1.817s console-setup.service
1.815s dns-clean.service
1.750s snap-gnome\x2dsystem\x2dmonitor-54.mount
1.699s snap-gnome\x2dlogs-43.mount
1.642s snap-gnome\x2dcharacters-103.mount
1.639s snap-gnome\x2dsystem\x2dmonitor-51.mount
1.609s systemd-modules-load.service
1.559s snap-core-5145.mount
1.218s snap-gtk\x2dcommon\x2dthemes-701.mount
1.107s snap-gnome\x2dcalculator-238.mount
1.048s systemd-random-seed.service
1.044s snap-core-4917.mount
1.033s snap-gnome\x2dcalculator-199.mount
964ms snap-gnome\x2d3\x2d26\x2d1604-59.mount
958ms snap-gtk\x2dcommon\x2dthemes-319.mount
934ms snap-gnome\x2dcharacters-124.mount
934ms dev-loop10.device
934ms grub-common.service
933ms snap-gnome\x2dlogs-37.mount
889ms wpa_supplicant.service
822ms dev-loop19.device
695ms swapfile.swap
686ms snap-gnome\x2dlogs-40.mount
540ms avahi-daemon.service
500ms dev-loop15.device
456ms systemd-journald.service
418ms user@120.service
415ms ufw.service
382ms apport.service
375ms packagekit.service
357ms gpu-manager.service
357ms speech-dispatcher.service
341ms gdm.service
339ms snap-gnome\x2dsystem\x2dmonitor-57.mount
337ms rsyslog.service
333ms pppd-dns.service
304ms systemd-logind.service
301ms snap-core-5328.mount
254ms systemd-remount-fs.service
245ms snap-gnome\x2dcalculator-222.mount
242ms snap-gnome\x2d3\x2d26\x2d1604-70.mount
228ms dev-hugepages.mount
207ms dev-loop8.device
198ms upower.service
183ms sys-kernel-debug.mount
173ms dev-mqueue.mount
170ms systemd-tmpfiles-setup.service
147ms systemd-timesyncd.service
134ms systemd-resolved.service
132ms systemd-udev-trigger.service
124ms kmod-static-nodes.service
118ms user@1000.service
104ms dev-loop17.device
104ms dev-loop16.device
103ms dev-loop14.device
103ms dev-loop13.device
102ms dev-loop12.device
101ms dev-loop11.device
101ms dev-loop9.device
100ms dev-loop7.device
100ms dev-loop6.device
97ms dev-loop2.device
97ms networking.service
90ms dev-loop5.device
89ms dev-loop4.device
89ms dev-loop3.device
89ms dev-loop0.device
88ms dev-loop1.device
87ms dev-loop18.device
74ms colord.service
60ms bolt.service
60ms polkit.service
59ms systemd-tmpfiles-clean.service
48ms systemd-update-utmp.service
43ms snap-gnome\x2d3\x2d26\x2d1604-64.mount
35ms snapd.socket
35ms systemd-rfkill.service
35ms resolvconf.service
33ms snapd.seeded.service
28ms systemd-backlight@backlight:acpi_video0.service
24ms setvtrgb.service
24ms alsa-restore.service
17ms systemd-backlight@leds:dell::kbd_backlight.service
15ms kerneloops.service
12ms systemd-backlight@backlight:intel_backlight.service
10ms ureadahead-stop.service
9ms systemd-update-utmp-runlevel.service
9ms systemd-user-sessions.service
8ms resolvconf-pull-resolved.service
6ms rtkit-daemon.service
6ms sys-kernel-config.mount
4ms sys-fs-fuse-connections.mount
My system isn't partitioned. Video card is Intel Mobile 4 Series Chipset; driver=i915.