Thanks to @chazaq @nephros and @pherjung or the valuable input, and to @ohnonot for the comic relief.
These steps did the trick:
- Add the xt9 repository with the information provided by @chazaq (subsituted armXX for aarch since it’s a different architecture), as the repo was missing from the local configuration as pointed out by @nephros
- Used pkcon refresh && pkcon install zypper && zypper install feature-xt9 as suggested by @pherjung
- Then installed Predictive Text Input from the App store (since the previous steps didn’t really do the trick). Now the feature is present. I am marking the thread as ‘solved’ accordingly.