Once you have found how long it takes for Linux Mint to Boot you can then find which programs / services are taking the longest to run by running the “systemd-analyze blame” command from a terminal prompt.
username@computername ~ $ systemd-analyze blame 12.157s dev-sda5.device 11.290s lvm2-monitor.service 10.284s ufw.service 10.001s systemd-journal-flush.service 9.879s keyboard-setup.service 9.693s run-rpc_pipefs.mount 9.684s systemd-modules-load.service 9.253s systemd-tmpfiles-setup-dev.service 3.073s NetworkManager.service 2.935s ubuntu-system-adjustments.service 2.399s networkd-dispatcher.service 1.722s udisks2.service 1.309s systemd-random-seed.service 986ms lm-sensors.service 967ms apt-daily-upgrade.service 964ms apt-daily.service 862ms fstrim.service 814ms accounts-daemon.service 667ms NetworkManager-wait-online.service 614ms gpu-manager.service 574ms systemd-fsck@dev-disk-by\x2duuid-000fff..... etc 537ms wpa_supplicant.service 535ms rsyslog.service 527ms grub-common.service 465ms upower.service 432ms thermald.service 395ms kmod-static-nodes.service 305ms systemd-udev-trigger.service 303ms home-username.mount 279ms systemd-remount-fs.service 260ms virtualbox.service 229ms polkit.service 226ms packagekit.service 220ms blk-availability.service 208ms avahi-daemon.service 204ms dev-mqueue.mount 187ms colord.service 176ms systemd-tmpfiles-setup.service 173ms systemd-journald.service 172ms alsa-restore.service 157ms apparmor.service 155ms systemd-resolved.service 147ms systemd-logind.service 141ms systemd-sysctl.service 131ms user@0000.service 129ms systemd-timesyncd.service 117ms dev-disk-by\x2duuid-00ff00ff\x0f... etc 111ms dev-hugepages.mount 109ms networking.service 89ms apport.service 80ms sys-kernel-debug.mount 80ms systemd-udevd.service 77ms setvtrgb.service 58ms systemd-update-utmp.service 53ms sys-fs-fuse-connections.mount 52ms lightdm.service 52ms rpcbind.service 50ms sys-kernel-config.mount 49ms hddtemp.service 48ms speech-dispatcher.service 47ms kerneloops.service 40ms plymouth-read-write.service 38ms systemd-user-sessions.service 37ms systemd-tmpfiles-clean.service 36ms dns-clean.service 26ms nfs-config.service 24ms console-setup.service 23ms motd-news.service 20ms home.mount 9ms rtkit-daemon.service 8ms ureadahead-stop.service 7ms systemd-update-utmp-runlevel.service 6ms plymouth-quit-wait.service 5ms openvpn.service username@computername ~ $
Once you have this (sorted) list and can see how long each program / service takes to start you can then start going through which programs / services you don’t need to start at boot time.