Betasom administrator

Unfortunately our installation has not been upgraded since 2013, so we have 4.3.6 installed. We are not able to make the upgrade to latest version as the upgrade needs php 8, but 4.3.6 do not work with it (only up to 7.4). How could we proceed for an upgrade? Is it possible to download intermediate versions and make an upgrade by steps or are there other solutions to try? Thanks