This is not something I can fix in uwot, but just in case people are searching for this, if you see the error:

Error in irlba::irlba(L, nv = n, nu = 0, maxit = iters) : 
  function 'as_cholmod_sparse' not provided by package 'Matrix'
Called from: irlba::irlba(L, nv = n, nu = 0, maxit = iters)

then if you are able to reinstall the Matrix and irlba packages from source as recommended at bwlewis/irlba#70 (comment), this will fix the problem.

If not, another potential workaround is to install RSpectra via install.packages("RSpectra") and it should be used in preference to irlba for the spectral initialization.

If you are also using PCA explicitly (e.g. init = "spca" or pca = 100), then the following might work: install bigstatsr (install.packages("bigstatsr")) and set pca_method = "bigstatsr".

For either of these you may need to restart your session and explicitly load them for this to work. I've had mixed experience with it (the install packages are eventually picked up).