In theory Russia and every other country already probably had the ability, Starlink uses comms in a standard frequency range, it's not really any different to jamming any other system (and jamming satellite broadcasts is old news, even modern satellites if you don't need those frequencies yourself).
The question is, can Russia do it without also jamming their own equipment, their own satellites and do it from a distance in such a way that it can't be compensated for.
IIRC a large part of Starinks usefulness comes from that highly directional comms, as it is by design and intention far less prone to interference from other users on the same frequency range and to have a higher number of concurrent users within the same frequencies than other systems (the only real way to do that is to make the areas which their communications are receivable in smaller*), which means that to realistically block it you probably need a much stronger signal that is somewhere in footprint of the satellites, and for starlink due to its intended use those footprints are quite small (very small compared to most satellites at only a few miles diameter).
In short basically in theory the ability has been there pretty much from day Starlink launched, but because of the highly directional nature of the system it's likely to require Russia actually have the hardware needed fairly near the terminals, which means that they might be able to jam right at the front lines, but 10 miles back it's going to be much harder (so a ground unit in contact with the Russians might be affected, the artillery 25 miles away could be fine, as could another unit only a few miles away).
I would also suspect that there may be a way for Starlink to compensate for it by changing which of any overlapping transceivers are in use to reduce the affected zone even more.
*The same idea behind having more lower power mobile phone transmitters in city centres and fewer, more powerful ones in the countryside, and why 5g is meant to be so much better (IIRC solid state phased arrays, so you can have thousands of people in a stadium with the beam being split into hundreds of very small locations so effectively there are only a small number of people using the frequencies per target area).
