I concur.
But now I started with unflagging the external HD I forgot to edit fstab.
UUID=c0d76448-59ba-48e6-b5e7-d5ed878a3193 / ext4 defaults 0 1
/swapfile swap swap defaults 0 0
tmpfs /tmp tmpfs noatime,mode=1777 0 0
/dev/sdb1 /media/pjw/ ntfs users 0 0
/dev/mapper/luks-d8f38af3-83a8-4dd7-a6e9-48e280799831 none ext4 users 0 0
So cleaned up fstab by removing the lines for sdb1 and luks.
UUID=c0d76448-59ba-48e6-b5e7-d5ed878a3193 / ext4 defaults 0 1
/swapfile swap swap defaults 0 0
tmpfs /tmp tmpfs noatime,mode=1777 0 0
And now initial boot-up is blistering fast, with a slight delay until login screen.
Mounting issues for the external drive are gone too.
Check on the external drive showed it to be fine. Still going to move its contents to a fresh drive.
I’ll do some more digging - like for the ‘restart icon’ keeping popping up - but for now it seems like a FU on my part. 
Your help was effective and very much appreciated.
You guys rock!