This is the reason behind the profiles like RVA23 which include bitmanip, vector and a large number of other extensions. Real chips coming very soon will all be RVA23.
The Milk-V Titan (https://milkv.io/titan) can take up to 64GB which is fine considering the number of cores and the cost of RAM. If you needed and could afford more RAM you'd be better off distributing the work across more than one board.
Unfortunately they found a bug and had to redesign the boards. I've had one of these on pre-order since last year. Latest is I think they're intending to ship them next month (April).