I find that everytime inpress the power button in unlock the screen which puts the notifications in the banner and I can’t see them anymore.
I know it’s like a silly struggle, but on other phones I’ve had you can easily check your messages without unlocking the phone entirely.
I don’t know about the fairphone specifically, but a decent amount of phones have pocket and pick up detection. They can detect when you take them out of your pocket or pick it up from like a desk and automatically turn the screen on, without unlocking the phone. There may also be a “double tap to wake” feature, which turns on the screen when you double tap it.
Both of these cause an at least noticeable decrease in battery life, but could be worth it if this is a big QoL thing for you.
If neither of those exist or you need the battery life, try only pressing the power button with your fingernail or sth, that’s what I did for some time and it worked just as well.