If you take the closest thing to a domestic itinerary we have in the UK with a tiny amount of added risk, it's to travel within the Common Travel Area. So, I've had a trip into Belfast, out of Dublin planned for a few weeks now. I'll be crossing the border between north and south either in a coach or a train - I've not decided which yet and I need to be as fluid as possible because if the south closes down further I'll likely just go straight to the airport and fly out.
The longest amount of time I'm going to be in Dublin is about 8 hours, perhaps as little as 90 minutes at the airport, yet now I technically need a LFT test 48 hours before to do that because although I'm coming from Belfast I'll also have been in the UK in the previous 14 days. That is bordering on the ludicrous, frankly, yet in the unlikely event I was approached by a member of the Gardai I'd be in a spot of bother.
So things change, and they rarely get cheaper or less hassle! If what is a near domestic itinerary can create a degree of inconvenience and cost, this really isn't the moment to go gallivanting to more exotic climbs ...