Unfortunately, my TV doesn't offer access to this setting. Been rummaging through the menus like a madman. No luck. Sounds like it is an easy fix for those with that option available, though. I will try it at family members' TV and their LibreElec boxes. But, at the moment I cannot confirm this solution. Luckily, I had success with the alternative solution offered by S80_UK.
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Thanks for chiming in. And you are right, indeed; my TV doesn't offer the option of enabling "just scan" or manually setting it to 16:9 or similar.
I've been looking for this (now painfully obvious) solution every now and then since august and intensively the last 2½ weeks. Thought I missed out on some Kodi lingo, since I couldn't google the answer. I'm relieved and embarrassed to learn that I can simply calibrate from within the player interface by accessing the settings - which I needed to do (once) for each change of frame rate (media, live TV, etc). Lovely. It works now.
A daily 'bug' in enjoying media - and an unjust and negative perception of Kodi in this matter - has finally been laid to rest on my part. Thanks for taking the time to share your knowledge.