I’ve got copyparty working behind a proper reverse proxy. This allows it to be publicly accessed using a nice domain name with SSL.

A reverse proxy (on a cloud VPS) re-directs the https traffic into my home lab where Copyparty is running on a Raspberry Pi 4:

Copyparty on a Raspberry Pi 4. It's in a grey and black metal case

Some geek friends of mine did some stress testing all at once on this Copyparty server. It could take a savage, nasty beating and survive. One tester had 1200 Firefox tabs open at once, hammering away. It was great nerd fun. It could continuously handle downloads at 45MB/sec. It never throttled.