Are you sure t-SNE and UMAP actually perform very differently? Last I looked, they were somewhat comparable.
[edit]: Seems they are similar for some purposes: https://blog.bioturing.com/2022/01/14/umap-vs-t-sne-single-c...
Also interesting: Rapidsai has a cuda accelerated version of umap that is very fast (hdbscan as well BTW).