The natural gas through the pipelines is not owned by the transit or endpoint country. Same with Nord Stream, Germany is used as distribution hub in central Europe. E.g. after Poland closed their pipeline to Russia, their natural gas supply from Russia was simply transferred via Nord Stream and Germany, from the other side across the border into Poland.
And even with natural gas that stays in German storages, it’s not owned by Germany. It’s owned by private companies that sell it during winter to the highest bidder. German gas storage can supply other countries that have high demand and smaller storage capacities in a cold winter.
So regarding the resource replacement, it depends on the country that uses the natural gas at the end.
Looking at natural gas in Germany, the usage for electricity generation is relatively low (~7-12% over the last 5 years). It’s more often used by the industry and for it’s chemical properties, as well as heating in homes. You cannot just replace that with coal or nuclear ovens. But overall there is a plan to increase the capacity for electricity generation over the next few years as backup for the coal phaseout during low renewable generation. The new gas plants are intended for natural gas and later hydrogen.