Everyone prefers more ports and having to use icebreakers costs money. But the question of ending up in the cateogory of land-locked counries if broken up - there are lots of ways you could slice it and still have sea access on at least one coast and probably on coasts outside the arctic as well. If they don't have good ports eg in the eastern side it's probably more lack of investment than access to waters.
(Though in such scenarios it would seem likely they'd still be able to agree to cargo transit through the newly estabilished neighbours)
Here's a map I found: https://www.searates.com/maritime/russia
Access to warm water ports has been a major driver in Russian foreign policy for centuries. Today they have access through Sevestapol and Novorossiysk on the Black Sea, and Mediterranean port access to Tartus in Syria. In the east the major port is Vladivostok which is kept open with ice breakers.
The security and economic consequences of lack of ports is a big problem. One of the major reasons they annexed Crimea was to guarantee access to the port without requiring a pro-Russian regime in Kyiv, but Sevestapol is now on the edge of a warzone with Ukrainian military just dozens of miles away and the administration not backing away from reclaiming their 2014 borders. Access to the Mediterranean requires bypassing Ukrainian security forces and the Bosporus controlled by Turkey, which is not allowing Russian ships through as a result of the war. To get goods or materiel through to Tartus they need to ship by rail through Georgia, Turkey, and northern Syria - again, major security problems.
So the only major port for Russia is Vladivostok which is across Siberia and ices over in the winter. That makes using it as a major shipping and naval hub prohibitive.
These issues have been around since Peter the Great expanded Russia into a global power, and even the Soviets struggled with naval power projection. Russia even more so today, and they're making their lives worse by invading Ukraine.