I have had the same experience as most of you. I cannot believe what having a smartphone has done for my concentration. I no longer feel absorbed in a book, or a film or tv programmes for that matter. I flit constantly and struggle with concentration.
I am working really hard to get back into reading. I am going to bed earlier and using the time for books. No phone allowed in bed. It has made a big difference and I am definitely getting back to being lost in the story sometimes.
You definitely need a really gripping read to get back in to it, plus some rules to make you have a good go. I have abandoned several books that I just couldn't get in to in favour of page turners to helps me stay focussed.
'This is Going to Hurt' by Adam Kay and Louis Theroux's autobiography kept me interested, as did Dolly Alderton's. Non - fiction is a bit easier to dip into in short bursts I find.
I've recently enjoyed books by Lisa Jewell, Liane Moriarty and Jane Fallon - all had good believable characters that helped me stick with it.
I feel like I'm on the road to recovery!
One thing it has made me really wary of is allowing my dc access to phones. Mine are too young at present but seeing what has happened to my formed brain with smartphones, it is terrifying to think what could happen to a young brain's attention span!