The BRICS alliance has all of the raw materials, chip manufacturing and manufacturing know how to build jets from 50-350 seats. They may not be as competitive in terms of efficiency compared to Boeing and Airbus, but they also won’t have anti-oil governments as a monkey on their backs.
Russia isn’t claiming they will go it alone. Just they are done with relying on the west.
There is a major flaw in all those "we'll build our own planes" supporting posts.
While I agree that Russians can build anything flying, and try to omit any modern technology (including, but not restricted to electronics, alloys and CRFP, high bypass gas turbines etc), and get something flying, you forget two major factors.
One is being able to put them in any reliable design. It's not useful to have a plane that is falling out of sky every year. And Russian planes (USSR built) have been known to fall quite often. Certainly even more so since they've not built anything new from the scratch and russian components.
Furthermore, I agree the problem will be tooling. They have hardly any manufacturing plants experience nowadays, since they were coming from West, ith advanced electronic components (soon to be dead), don't have technologies and would need to do most of the work with handworkers. Plus, limited resources will need to be shared between different machines/products (what is your priority, tanks, or cars, planes or ships, manufacturing plants for bricks or steel milss, military or civil?). While I fully agree they would be able to design an aircraft, I doubt they would be able to get it running into numbers for a reasonable time. There will be nothing but shortages between markets, certainly. And other markets will have prioirty to access whatever components are required.
So, for me it's all clear: while we can argue it can be designed/built, it will not be taking over the work from western airliners, period. That's just impossible, even with "friendly support". It wasn't possible to build all necessary extra (additional) capabilities, since it was easier to buy these western, and any remaining would not be spared on new planes, and everything Russia would need. Higher priorities are down the queue, and resources are limited for quite a time.
That's my 2 cents.