You can't. Nothing beats first hand knowledge. What I do is I put some demos of content on a USB stick then I go to local TV shop and try them out and play around with the TVs. Or if the store is good with returns you could always order it home and play with it and usually you have 14 days to return it, but that's very much dependent on shop policy.
Don't trust in spec numbers, because they are misleading. Like you will see TVs with many more local dimming zones but they end up performing poorly because the algorithm can't handle it properly, and to see an extreme example look at something like TCL 8 series (X10 in EU) which has 1000s of zones vs a higher-end Sony LCD with like 48 zones and the Sony still does a better job. Look at this, black crush for days (at 4:01)
not to mention how horrible the colours are.
X10 vs XF90 (look at the zone difference - and it means nothing!)
If you want just the numbers then have RTINGS.com as a reference, and become very good friends with that site. It will provide you a good overview of just tech specs but DO NOT TRUST their scores (they give a grade for each category) - they are very stupid! Another thing to be aware of is that sometimes you'll see measurements in one mode over the other but the TV doesn't behave the same in both modes, that's why I recommend Sony so much - there are no such shenanigans.
At the end of the day, yes, you do have to research the TVs individually. But cheer up, there's usually little choice in Europe (LG OLED vs Sony LED vs Samsung QLED), and if you don't want to spend a lot then the choices are even fewer.