What data type(s) in those columns, and what locale on each server? Maybe the change from 18.04/12 to 22.04/15 has caused some weirdness with "foreign" characters.
The data is UUID strings (typical alphanumeric characters and hyphens) stored in varchar(36) fields, a few booleans and an int. Nothing exotic/weird/foreign to a US-based observer. The DBs are both using UTF8, the LANG env is set to "en_US.utf8" in both sides as well. The primary key fields are those varchar fields storing UUID strings, not using a sequence or any type of auto-incrementing value.
