Beepbopboop and Ade seem to indicate that some people realise the th sounds as dental stops. This is something that I hadn’t been aware of but it is mentioned in this Wikipedia article https://en.wikipedia.org/wiki/Th-stopping. "Th-stopping is the realization of the dental fricatives [θ, ð] as stops—either dental or alveolar—which occurs in several dialects of English. In some accents, such as of Indian English and middle- or upper-class Irish English, they are realized as the dental stops [t̪, d̪] and as such do not merge with the alveolar stops /t, d/; thus, for example, tin ([tʰɪn] in Ireland and [ʈɪn] in India) is not a homophone of thin [t̪ʰɪn]." So it seems this is a phenomenon among some middle-class Dubliners.

Outside of middle-class Dublin, there are some other areas where you will occasionally hear people pronounce soft d and t as dental fricatives.

Broadcasting: Even local radio stations tend to only hire broadcasters who pronounce soft d and t as dental fricatives, even if they otherwise speak with local accents.

People (mostly women) who received a convent education: The nuns did a lot of good in society but some of them nonetheless seemed to have had a particular disdain for regional accents, and especially for the fact that people didn’t distinguish soft d/t from hard d/t. So, they went to war on regional accents under the guise of “elocution lessons”. I remember my sister learning the following rhyme in her convent primary school: “This, that, these and those; that’s the way the ‘th’ goes.” I think this has influenced how some people pronounce ‘”th”. However, for such people, they will often pronounce “th” inconsistently. For instance, maybe 10% or 20% of the time they will pronounce it as a dental fricative but, the rest of time, they will revert to type. (This reminds me of a video I saw from a college Irish course, where the lecturer would pronounce Irish soft c as hard c most of the time but the odd time he would pronounce it correctly as soft c, almost as a mere token effort.)

Lastly, I suspect there are some people who consciously change their pronunciation of soft t and t to a dental fricative in order to appear “educated”, possibly through the influence of television. I suspect there are also some youtubers who do this because they want to appeal to an international audience and who fear that, if they don’t do so, foreigners will have difficulty understanding them.

Despite all these exceptions, I think the majority of people in southern Ireland still pronounce soft d and t as if hard d and t respectively i.e. as alveolar plosives.

Thank you for the explanation. There are many people in England who pronounce th as either f or v, eg another = anuvva.