Hello Patrick and Paul,
Thank you for info about StakingTool - this tool confirmed that it is possible to build the stack using switches I mentioned.
In fact, I was able to build such a stack "in real life" today with properly elected X460G2 nodes as master and backup and X440 nodes as standby. The only difference is that I was using exos 16.2.1.6 image on all nodes - StackingTool says 16.1 is the max. hardware supported version (?), I guess this needs updating. Stack didn't come up automatically, I have to make some extra configuration steps manually, but then I got full ring topology.