score:3
According to Timatic's COVID travel information page:
- Passengers are not allowed to enter. This does not apply to:
- nationals of the Russian Fed. and their family members;
- permanent residents of the Russian Fed.;
- British nationals and residents of the United Kingdom if arriving from the United Kingdom;
So you can indeed enter Russia at this time. You will use your British passport to prove you're a British national and then use your Israeli passport to gain visa-free entry. Showing two documents at once at immigration is common practice, so airline personnel shouldn't give you trouble for it. The Israeli passport will serve as an equivalent of a Russian visa, allowing you free passage.
Update: OP was able to travel successfully:
@JonathanReez it worked! They asked me for both passports both times, just like you said, and it all went without any disturbances!