It's not about transitioning to 100% renewable in this context, but about having a good enough supply of renewable energy to be more independent.

Are you talking about any specific part of Europe? In Sweden I think natural gas is supposedly something like 3% of totalt energy expenditure, although it is important for heating in some areas and dearth would affect that a lot i assume.

With current tech you can get fairly easily (not necessarily cheap) to 80% renewables penetration in Europe. The rest of the 20% could then be covered by coal, gas, biomass and nuclear.

Mind you if the goal is to get Russia out of the European gas market, by greatly increasing the amount of renewables we use the rest could be supplied by LNG + Norwegian/Dutch/English fields.