For non output tubes sometimes a gain tube is followed by a cathode follower which is sort of an electronic transformer to lower the output impedance of a gain tube so it drives the next gain tube better. Goof examples are 1970s and 1980s Audio research amps and preamps.. This effectively can double the small tube count.
Another possiblity(which can be also combined with cathode followers) is push/pull voltage gain stages. This doubles the number of small tubes also. Again look at the Audio Research products from the 70s and 80s. Push/pull needn't be used for voltage gain even with push/pull output amps. And many preamps are single ended too even from manufacturers who made push/pull tube output amps.
Another possiblity(which can be also combined with cathode followers) is push/pull voltage gain stages. This doubles the number of small tubes also. Again look at the Audio Research products from the 70s and 80s. Push/pull needn't be used for voltage gain even with push/pull output amps. And many preamps are single ended too even from manufacturers who made push/pull tube output amps.