In global business, the seller determines the currency that the buyer must pay to purchase their product. Not the other way around. There is currently no way for the EU to substitute Russian gas. The infrastructure for large scale LNG distribution simply does not exist in the EU. Also there aren't enough ships in the worlds to transport the necessary LNG to the EU anyways. Building the necessary infrastructure would cost hundreds of billions and take 5-10 years. On top of that the LNG itself would cost several times more than Russian gas. It's simply not feasible.
Some countries have already agreed to pay in Ruble but it's not as simple as that. The more important aspect is that hostile countries must now setup Russian bank accounts to make payment deposits. In actuality the buyer can pay in Euros and then the Euros are converted into Rubles in Russia. Once the Rubles are received, the transaction is considered complete. In this way the EU countries can save face as well by saying that they've defied Putin and that they're paying in Euros when in fact the Euros will be converted into Rubles anyways.
The reason the buyers have to setup accounts in Russia ? Well that's obvious. In the last few weeks the west has frozen hundreds of billions of dollars worth of Russian assets abroad. Therefore if the EU countries do not setup Russian bank accounts, what guarantee does Russia have that the west won't simply freeze Russian assets abruptly ?
In regards to the Turkish economy, there's no way to paint it in a positive light. Turkey is a net importer and because the currency is so devalued, it doesn't even make sense to use it anymore. Exporters pay for raw materials in foreign currency and sell the finished product in foreign currency, avoiding the Lira as much as possible.
Inflation is at 60%+. 2/3rd of cash transactions are in Euros or USD. The only reason the Lira hasn't completely collapsed is because the government is pumping billions into keeping it afloat. However unlike Russia, Turkey doesn't have a large war chest of foreign currency and gold reserves. Right now the Turkish government only has enough foreign currency to cover two months of electricity needs for the nation.
The Europeans have lost their minds. Gas prices have gone up by 4x in the UK. Petrol prices are completely unaffordable even for most middle gas in the EU. Food prices are about to go up as well since wheat prices are at an all time high and fertilizer prices have also gone up by 4x. Many economists are predicting a recession in the next year or two.
Look at this clip. This is Margrethe Vestager, European Commissioner for Competition recommending that Europeans cease taking showers in order to stick it to Putin. I don't think Europeans realize that if Russia turns off the gas, they will go back to the stone age without electricity or industry.