Having just listened to the Godowsky sonata and then doing a search on it, I came across this post:
https://www.pianostreet.com/smf/index.php?topic=61595where these pieces are listed:
Godowsky - Sonata in e minor (1910)
Dukas - Sonata in e-flat minor (1900)
Reger - Variations and a fugue on a theme by Telemann (1914)
I'm kind of blown away by the Godowsky sonata - 5 movements, 45' duration - maybe not easy to learn and keep active in the repertoire, not easy to program, but definitely a work of musical art. Now with historical hindsight, the epoch of the Epic Sonata was not long live, but there are probably some hidden gems from that period. I've come across these pieces, though haven't listened to them:
d'Indy - sonata (1907)
Rachmaninov - sonatas (1907 and 1913)
I'm wondering if anyone is familiar with the above pieces and can comment on them, and other Epic late romantic sonata-scope pieces you might be familiar with, focusing more on the lesser known one-off's, rather than prolific sonata composers like Prokofiev, Scriabin, Medtner.