At present (and unhelpfully) there are two forum discussions about much the same problem with the speed-limit warning system (ISLA) that seems to afflict only the very latest Hyundai 10 cars. There's this discussion and a second longer one that began a month earlier (link below)
https://www.hyundai-forums.com/thre.../threads/speed-limit-warning-national-speed-limit.705626/#nested_reply_top_post
I understand that the latest i10s can have a built-in sat-nav system (optionally?), but I don't know if the i10 owners who are complaining have sat-nav on their cars or not. And, as I can't find on-line an Owner's Manual for 2023 i10 models, I'm not aware of what Hyundai says about these cars' ISLA, nor - when an i10 does have sat-nav - whether this may be linked to the speed-limit warning system.
As I said on the other forum thread, I gained the impression that the i10's ISLA was unable to recognise the UK's national speed-limit traffic-sign
and, consequently, the ISLA continued to assume that whatever speed-limit (30mph, 40mph, etc.) that the system had been able to recognise had not changed. However, that assumption would be easy to check, as UK urban areas will generally have a 30mph-limit sign on the way in and a national speed-limit sign on the way out.
If the latest i10's ISLA is actually unable to recognise the UK's national speed-limit traffic-sign, that's clearly a fault with what is supposed to be a valuable 'safety' system and that fault will need to be corrected by Hyundai via their UK dealerships. In your case, it's the responsibility of the dealership you bought the car from to investigate/cure the fault and your more local dealership may be less interested in putting in effort. But you should certainly contact the local dealership about it as it's a warranty issue and - if they also say they've never heard of the problem - you can point them to these two forum discussions. (Print them out if you can...)
It's probable that, if any of the i10 owners who have complained about this problem in the two forum threads have had the issue satisfactorily resolved, they would have provided a follow-up - so I believe you can assume that a 'fix' is still not forthcoming.