DH and I have just had Covid and have a toddler dd 21 months.
Where we live we don’t have to isolate, although between feeling rough and feeling guilty we pretty much did for a week, a couple of times I pushed her out in her stroller, making sure to stay on the opposite side of the road to anyone else, as it’s the only way she’ll nap.
playdough is a good one here, needs supervising so she doesn’t eat it but it keeps her pretty busy. She’s also obsessed with stickers so I got quite a few reusable sticker books from Amazon - we had got her one for Easter anyway, and I ordered a couple more when I saw how well it went down.
If you have a full length window/ glass door anywhere you could get a spray bottle (clean if it had product in before) and get them to spray then you can stick foam letters/ shapes to it. She really liked that - you could do it on the side of the bath or maybe bathroom tiles too? Or in the bath? Baths in general - loads of containers, bubbles, bath crayons, play music, dim the lights and bring any light up or flashy toys in to the bathroom to make a ‘disco bath’.
Pile any cushions, pillows, plus size soft toys, sofa cushions etc onto the floor and cover with a sheet for a mini obstacle
course/ soft play.
Big storage tub, fill with pasta or lentils or rice or whatever you have and various containers/ scoops/ toy vehicles etc. Or do it with water. A good way to keep mess contained it get a fitted sheet, stretch it out sort of upturned and put a chair at each corner - keeps all the mess contained in there (in theory anyway).
you can get busy boards and things with different buckles, clips, buttons and zips to fiddle with from Amazon for about £12 - tjat
kept ours busy for a bit.
Standing at the sink washing up usually goes down well here too - we have a learning tower thing someone made for us but you could use a chair if you supervise.