Post [Br]exit wondering if extra time needs to be allowed now for border crossings driving from Dublin to north Donegal? Better to just stay in the Republic?
No, there should not be any issues. NI continues to follow EU rules and regulation in order to keep the Irish border open.
Both countries remain part of the Common Travel Area meaning people can freely cross the border. Other than a sign saying “Welcome to Northern Ireland” you probably wouldn’t realise you were crossing a border.
Road signage will change but other than that you’ll not notice anything different.
You do need to think in miles per hour and distance in Northern Ireland, and kilometres per hour and distance south of the border.
there are no border controls NI is part of the UK and the UK and Ireland have a common travel area like the others have said the only thing you will notice is a "Welcome to Northern Ireland" sign remember the road signage is all UK road signs and the speed limits are in miles per hour also you will need UK pounds for Northern Ireland
When are you planning this trip? You may want to re-evaluate this in view of the UK's latest quarantine rules. I have no knowledge of how those rules will affect the NI-ROI border, but it stands to reason that if the UK is requiring travelers to quarantine and have repeated tests, they wouldn't let people drive into NI from ROI without some kind of controls, because once in NI, someone could try to circumvent the quarantine by boarding a ferry to Great Britain.
I'm sure there are others on this forum who may know about how this is going to work. The following article is a couple of weeks old, but it goes into detail for ROI. https://roscommonherald.ie/2021/01/25/explainer-the-debate-over-covid-19-travel-and-quarantine-rules-in-ireland/