How to set up NAT for multiple routers?

Question

Mikrotik

Good day!
Configured NAT on Mikrotik (M-OSPF-15). The router goes to the Internet (pings ya.ru, vk.com, etc.).
It is necessary to configure Internet access for all routers from the OSPF zone, since now other routers do not have such an opportunity (they do not ping ya.ru, vk.com, etc.).
The option of forwarding the default route to the router that feeds the traffic (M-OSPF-15) is out of the question, maybe. there can be only one default route, and there can be several routes to M-OSPF-15.

I work in the EVE-NG virtual laboratory.
PS: I'm just versed in networks, if there are any details missing - write. Explained as best I could.

Answer 1

The option of forwarding the default route to the router that feeds the traffic (M-OSPF-15) is out of the question, maybe. there can be only one default route, and there can be several routes to M-OSPF-15.

What is the problem with the same OSPF to announce the default route? And what side is nat here, if your routers stupidly do not know where to send all the traffic?