Migrating an EU citizen to join adult children in the UK

I would be grateful for any advice about moving a retired EU citizen to the UK to join the rest of their family (children/grandchildren) who are all British citizens.

A is mid-60s, retired, and a citizen of an EU Member State but has been spent most of their life living in a country outside of the EU. They are married to B who is also an EU citizen but living with A in a non-EU country. A and B own property in the EU country of which they are both citizens and – over the last 10 years – have visited 5 or 6 times every year. Their plan was to retire to this EU country in the near future.

A and B have two adult children who are both settled in the UK and have had UK citizenship for a number of years.

B has just died unexpectedly. A immediately moved back to their home country within the EU. However, following B’s death, it is no longer certain that A will want to retire there in the long-term. From a family point of view, it makes more sense for A to be living in the same country as their children and grandchildren. All A’s close family live in the UK. A is very much independent and so could not easily be described as a “dependent relative”.

In the event that A wanted to move permanently to the UK – or at least maximise the amount of time they spent there – what is the most obvious route to make this happen?

Does the EU Settlement scheme have anything to offer under these circumstances? If not, how is this situation navigated by UK citizens wanting to support an older relative from non-EU countries? I seem to see this happen a lot in some communities and so clearly we aren’t the first family to end up in this position.

I suspect that, without Brexit, this wouldn’t have been a problem at all and A could have come and gone at their leisure. But we are where we are.

Any thoughts would be very welcome.

Simplest would be:
- EU citizen "A" should arrive before 31 December 2020 as there's still Free Movement until then.
- Establish residency in the UK, i.e. arrange NINO, Bank account, bills, etc - establish paper trail which proves arrival before 31. Dec.
- Apply for Settled Status in the UK - the deadline for this is 30 June 2021 - recommend it's done as soon as possible to avoid delays.
- "A" receives pre-Settled Status and can apply for full Settled Status (permanent residence) after five years
It's very difficult for UK citizens to sponsor parents under UK immigration regulations, very expensive as children are required to provide funding, especially for health care, and there won't be any settlement rights.
I'm sure there will be more detailed responses but that's about it in a nut shell.

Alternatively, as a non-visa national "A" could visit for 90 days in any 180 days period - it's visiting only.

A should go to the UK and start settling there before the end of this year 2020 then apply under EU Settlement Scheme ASAP.

If the move is not done before Dec 31, 2020, this project may become not feasible.

Thank you, both.
It sounds like a "no brainer".
Now to convince A.