We have been accepting questions about Quorum for some time. Although it is clearly different in non-trivial ways, it is Ethereum-like with a few twists. While there is a modest risk of losing focus, I think the benefits of consistently accepting questions about EVM variants outweigh the concern about noise.
Questions about ETH 2.0, which is less like Ethereum 1.0 than most of the variants we're talking about, seem to be acceptable. In a similar vein, there are adjacent technologies, like layer-2, automated market makers, oracles, etc. that Ethereum developers may have questions about. I don't find those questions inappropriate and this is the go-to place for answers and friendly help.
Competitive chains might seem like adversaries to Ethereum but I don't think this community should carry that torch. We should be supportive of developers working in this field and the reality is that clients ask about deployment platform options. This should be a place to get answers.
It would probably be very beneficial to establish some tags for other chains and technologies (as we have done for Quorum, Uniswap, etc.), to clearly show when questions/answers might pertain only to a particular environment.
In summary, I incline to an inclusive scope rather than an exclusive focus.