I’ve investigated this a bit further and found out, that the highlighting does appear only when a SIM-card is inserted into my phone. If I remove the SIM-card and delete the app storage for Summit, the highlighting is gone. Changing the locale didn’t seem to have an impact on this. Maybe this helps.
I have a OnePlus 8 running Android 13 (LineageOS). I could replicate this on another phone also running LineageOS.
I would greatly appreciate that, thank you. Love the app so far.