To share files in a local network FTP or SMB/CIFS may be better suited.

IPFS is content addressable storage by design on entire files. Reading limited set of chunks poses some problem regarding data integrity and deduplication colisions. One bit flip in JPG may destroy the entire image - thankfuly with currently used hash functions the right and broken files will have different "fingerprint". One way hash functions have extremely low probability of collision with full file scan. However when you skip part of files the probalibity of collision is roughly equal to count of bytes not scaned divided by total file size.

It’s a shame modern file systems don’t generate and store common hash algorithms as file metadata.

Some file systems like ZFS, btrfs support checksum on block level. However file level checksum is not trivial with random write file system. Imagine 1 byte is changed in 20GB file - that would require full file scan to update the checksum. Recalculating a file checksum from all block checksums could be a solution however far from any standard.

Wouldn't a merkle tree, like torrents or dat use, avoid this? You'd only have to generate a hash of the changed chunk, then it's really low cost to update the root hash.

https://datprotocol.github.io/book/ch01-02-merkle-tree.html

Yep, my last sentence covered also Markle tree.

I don't understand why you got impatient? Just let it finish and then you can share, easily enough across your entire network.