The only folky activity I've heard of is the festival in July
www.folkonthefarmfestival.com/

&

Môn Folk Plus
first fridays
open mike format
"a range of musical genres and performance poetry,,, and we live in hope of attracting a unicyclist very soon."
https://facebook.com/groups/1545011952445790

Pilot Boat,
Dulas LL70 9EX http://www.robinsonsbrewery.com/pilotboat
+44 1248 858260
https://facebook.com/profile.php?id=100057229788214

https://maps.google.com/?cid=1994231620409070634

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It'd be worth asking on
Folk Sessions in North Wales
https://facebook.com/groups/151821118246386/

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Otherwise on the mainland the closest seem to be

Clwb Gwerin \ Conwy Folk Club
weekly Mondays 8pm
mostly singaround, occasional guest night

& some around Porthmadog.

(Folk Club Map - open in a browser)