This question is in the past tense so basically theoretical.
My trip started in the U.K. in May. Two weeks later, I went through a facial recognition with boarding pass check, security , and a later immigration stop (and stamp) to leave the U. K. for Dublin, as well as one to enter Ireland upon arrival. All as expected.
In June, I took a ferry Dublin to Holyhead. Although I needed to present my passport at the ferry check in, there was no separate immigration process.
When I arrived in Holyhead, absolutely no process there. We just got off the bus from ship to terminal and left.
I then flew out of Manchester to Venice a week later. No separate immigration process to leave the U.K. (Just the facial recognition with boarding pass. But that is just before entering security.)
There was a fast normal process to enter Schengen in Venice.
Has it gone digital in some places? There were 3 places I expected SOMETHING that I didn’t encounter.
I am basically just curious.