Uguu: simple lightweight temporary file host with support for drop, paste, click and API uploading.

This one is p2p: https://github.com/schlagmichdoch/PairDrop (or just try it in https://pairdrop.net/ )

But that also means that you need to keep the page open while the other device downloads.

Another p2p alternative is using webtorrent: https://instant.io/

https://github.com/eikek/sharry

Disroot offers temporary file sharing. Files are shared for 24 hours, 7 or 30 days with optional auto deletion, and password protection. You can also self host it if you want.
https://upload.disroot.org/about

Uwu (that's how is spelled in Spanish)

I like gofile.io. 🤷‍♂️ Not self-hosted but hey.

Or like ones that are written in a modern memory safe languages?

Do you mean something like Rust?