Rural walks nearish to Dublin

It's coastal, but how about Howth?
https://www.youtube.com/watch?v=qNtvsxil2Mc&t=1760s
Here is some information about walking in the Boyne Valley (Drogheda has good access):
https://www.discoverboynevalley.ie/guided-and-self-guided-walking-trails-boyne-valley-2023

Thanks for the links! They both look good.

You mention Glendalough. In 1999 over seven days, I walked the 100-mile-long Wicklow Way trail (https://www.wicklowway.com/) that goes through Glendalough. You could access the trail and go either south or north from Glendalough: https://glendalough.ie/. As you head south, there are two glacial trenches any fit hiker could handle and then it becomes farmland. Also, you could start the trail in Dublin at Marlay Park (https://www.dlrcoco.ie/parks-outdoors/parks/marlay-park) and walk for four to six hours.

I did part of the Howth walk a few months ago. (I only did part of it because when I got to the top it was so windy it was raining sideways). There are a number of trails/walks of varying lengths. One of the longer ones starts right opposite where you come out of the DART station. It takes you up and through a residential area and then puts you out in the area by the cliffs. You can also walk through Howth from the DART station, past the harbor, up Balscadden Road, and start the cliff walk there (which is what I did). Even with gray, drizzly weather the views were beautiful. This walk is mostly coast, so it may not be what you're looking for. But it's super convenient to Dublin.

Thanks to you both for your input. Wicklow thru Glendalough does look like a good option. Do you think I'd have a problem getting a taxi back around sunset from one of the small towns along the way?

Howth does look enchanting. I might be able to fit it parts of it on another day. Fingers crossed.

I believe you could get a cab, but that's only a guess. The reason is because Glendalough is a top -- and worthwhile -- tourist draw. In addition to the natural beauty, Glendalough, an ancient monastic site, features amazing antiquities. St. Kevin founded the monastery more than a millennium ago. Structures like an ancient Celtic church called St. Kevin's Kitchen are incredible. On a more practical level, Glendalough is roughly 25 miles from Dublin. I know for a fact that public buses run between the site and the city because I saw them, so cab service is likely. And tourist agencies charter buses from the city and back throughout the day. The Dublin tourist information office in the center of the city not far from Grafton Street would know for sure about cab service.