Samsung has introduced an ultrasonic fingerprint sensor in its S10 phone. This is not repairable at all:
If Samsung has any repair tips they’d like to share, we’re all ears. For now, assume you’re going to pay an arm and a leg for a new screen should the sensor malfunction.
… and they do malfunction to the point where:
Low fingerprint recognition rate has led some to call feature a “technical defect”
As per iFixit’s request, some tips are offered 
Numerous Galaxy S10 users have posted messages to Clien and other smartphone user community sites sharing their experiences with fingerprint recognition failures. Some have gone so far as to call the problem a “technical defect.” Tips for increasing recognition success rates have also been shared. One example read, “Rub nostril grease or spit on your finger before you use the recognition feature, and press hard.”
Experts said the Galaxy S10’s low fingerprint recognition rate appeared to stem from the technical limitations of ultrasonic fingerprint sensing. The technical characteristics of the ultrasonic approach are such that the rate of recognition decreases when air is present between the finger and the sensor.
“It’s the same reason that they apply gel when they do ultrasonic testing on your abdomen during a health examination,” explained one expert.