Mixing oils and a modern varnish seems to be a preferred, "state of the art" finish. since it combines both a rubbed oil finish and the hardness and protection of a polyurethane finish. Before polyuruthane, spar varnish was often used.
My grandfather built a cabin back in the '20s. The interior wood was finished with a combination of linseed oil, terpentine (to thin the oils so they penetrated better) and either shellac or varnish, depending on who you talk to. The walls are still in great shape, over eighty years later.
Tough stuff!
David L