Coax, if you mean via Virgin Media (formerly UPC) could be an option.
I know some places got left behind when they upgraded their backend networks to Fibre, and for one reason or another they don't offer any Broadband in these places. Of course, these tend to be places without Fibre from Eir as well - probably due to lack of conduits for cable routing.
Where they do offer broadband though, it's miles better than old copper phone lines and reliable - worth looking into.
Their website has a Eircode checker that i think is accurate, as is Bonkers in my experience (if you haven't checked already)
pageInfo.description
www.bonkers.ie
It will show the 4 main wired broadand networks availability.
Virgin Media - Generally good with some variance
SIRO - Fibre only, so great
openeir fibre - Fibre only, so great
openeir legacy - Varies massively - totally dependent on phone copper wiring, exchange, distance etc.
Dublin City North to me seems like a good spot to try out 5g. I'd imagine you have multiple providers to pick from if you can position the modem in a good window high up.
You can see some crowd sourced data that seems accurate here (for signal at road level most likely)
Compare the network coverage of mobile operators and check their performance at home !
www.nperf.com