I just flew this route a few weeks ago. I made a trip report here:
TAP UK - Brazil J class review during COVID. A330neo, A320, ATR72.
I really enjoyed TAP on the whole.
I've read online they aren't great when it comes to sorting out a refund (though they aren't alone when it comes to airlines and COVID related refunds). However, I found them really flexible when it comes to making changes to dates and even departure cities.
Travelling is a nightmare at the moment - period. For me the biggest stresses didn't come from the testing requirements etc. The main issue is the constantly changing border requirements. We had to change our whole itinerary about three or four times before flying because of this.
Saying that, you can book this and fly the Brazil segments as far away as November. I'm cautiously optimistic that things will be very different by then. Not so sure about having to complete the flight to LIS from europe by end of May though, especially if you are originating in the UK.