If anyone is genuinely curious about this, they were indeed letting Russian gas through and stopped in 2025:

> On 1 January 2025, Ukraine terminated all Russian gas transit through its territory, after the contract between Gazprom and Naftohaz signed in 2019 expired. [...] It is estimated that Russia will lose around €5bn a year as a result.

https://en.wikipedia.org/wiki/Russia%E2%80%93Ukraine_gas_dis...