Samsung does a commendable job of updating its older flagships with features from newer releases. The Galaxy S20 series' One UI 2.1 firmware has already made its way to Galaxy S10 and Note 10 phones. Initially, it was rumored that Samsung wouldn't make it available to the Galaxy S9 and Note 9 series. Some unverified rumors and speculations later, it is now confirmed that the One UI 2.1 update for all three devices is under development.
The information comes from a Korean Samsung Community forum moderator, who says that the software development process is 'under review.' The post also states that the update is being developed for both Korean and global versions of the devices. It rounds things off by saying that the test builds of the One UI 2.1 update should be available to users soon.
Technically, there is no reason for Samsung to deny Galaxy S9 and Note 9 users the One UI 2.1 update. The phones are more than capable of running the software, and features such as Quick Share and Music Share will bring them on to spec existing Samsung flagships. If things go smoothly, we can expect to see a worldwide rollout commence within the next month or two.