The old English 'ᵹ' has visual similarities with the Georgian 'გ', also our 'g'.
We've two letters that are visually similar to yogh 'ȝ': 'ვ' (an English 'v', or 'w' if you're Tbliseli), and 'პ' (a hard 'p'). Our 'gh' sound is 'ღ'.
ᵹ has a clear line of development back to capital "G": https://en.wikipedia.org/wiki/Insular_script#/media/File:Evo...
And AFAIK Georgian alphabet predates Insular script by a few centuries.
It's not uncommon for otherwise unrelated alphabets to come with similar symbols simply because the trend over time is towards simplification of letter shapes, and there are only so many basic elements. So even originally quite different characters can end up looking very similar when reduced to a few squiggles.
If you start looking into it, you will surely be astonished at just how much “cultural exchange” there must have been going back even into the Paleolithic time, and definitely during the period of the OP article is touching on.
People have an extremely distorted perspective on European history for many reasons, but the late industrial age nation state probably had the biggest impact on that mental model people still have today in many ways. By all evidence I’ve seen, the cultural exchange in the distant past was far more organic than most people can easily imagine today for many reasons. Trade and cultural communion, religious exchanges and defensive unions all made that possible in a world that was not at all as controlled and authoritarian as we even experience today. It all waxed and waned over the centuries and regions of course, in a rather organic manner; but due to practical limitations a lot of the authoritarian restrictions we are all subject to today simply did not exist.
In some ways the USA until about 1960, is probably the most similar analogue of how Europe seems to have generally been for the longest time leading up to the Industrial Revolution. It was a land of general regions of self-regulating, cultural clustering with local levels of varying jurisdictions and power structures which to a large extent kept most people in their home region, if not their place of birth. By the latter part of that period the identity with one’s state and region and local culture had already largely succumbed to the oppressive force of the centralized dominating power of the federal and global power, but your region was still largely your cultural identity as a person and community.
That of course has all been totally razed and destroyed now and the USA effectively exists in name only today, which has been the case for an even longer time, but that’s a different topic altogether.
Took me a couple of seconds - Georgian .. as in the other country with a red cross on a white background (although you add a few extra crosses than England)
I have no doubt that two very disparate languages and scripts will find a few similarities simply due to proximity. Georgia and England (UK) are close enough for a fair amount of cultural exchange.