I'd agree with you, it's not really a notable claim.
Or at least the question hasn't shown that it is; the fact that multiple factcheckers - eg 1, 2, 3 - covered the issue might show notability (the fact that all google results for "russia lion covid19" are about how it's not true shows that it is a boring claim).
As the question has now been seen 18k times, I guess it can be argued that it's in either case a notable claim now.
Regarding notable vs reliable: Sources in questions are to show notability. They do not need to use reliable sources, though they shouldn't use satirical sources if they can't show that people actually believe it for some reason (an article from the onion for example would not show notability; if a well-known politician were to pick up their story and talk about it as if it were fact, that would show notability - even if the politician isn't reliable).