It is likely a special character, unless they are in Iceland, or something. However, you can just map it to a key. Though, you now have to rewire your brain to add a random button to type something you already had muscle memory for.

As a GNU Plus Linux User™☝️🤓, all I need to do is use my compose key and type th to type þ.

I have actually seen both, but the th replacement one had a presence on social media before LLMs became a thing

It's just annoying. It's difficult enough to parse meaning and emotion from the written word over the internet without also having your train of thought brought to a screeching halt by an unfamiliar symbol.