Reverse_proxy for Browser-based compiled Minecraft client using WebSocket not working

I’m using a different hosting platform now that runs on Ubuntu.
(Everything below is regarding that, posts above may no longer be a concern.)

This is the error I receive:

443 port already in use
root@ifsmp-proxy:/home/ubuntu# caddy run
2023/01/10 22:55:59.734 INFO    using adjacent Caddyfile
2023/01/10 22:55:59.736 INFO    admin   admin endpoint started  {"address": "localhost:2019", "enforce_origin": false, "origins": ["//localhost:2019", "//[::1]:2019", "//127.0.0.1:2019"]}
2023/01/10 22:55:59.737 INFO    http    server is listening only on the HTTPS port but has no TLS connection policies; adding one to enable TLS {"server_name": "srv0", "https_port": 443}
2023/01/10 22:55:59.737 INFO    http    enabling automatic HTTP->HTTPS redirects    {"server_name": "srv0"}
2023/01/10 22:55:59.737 INFO    http.log    server running  {"name": "remaining_auto_https_redirects", "protocols": ["h1", "h2", "h3"]}
2023/01/10 22:55:59.737 INFO    http    enabling HTTP/3 listener    {"addr": ":443"}
2023/01/10 22:55:59.737 INFO    tls.cache.maintenance   started background certificate maintenance  {"cache": "0xc00047b500"}
2023/01/10 22:55:59.737 INFO    tls.cache.maintenance   stopped background certificate maintenance  {"cache": "0xc00047b500"}
Error: loading initial config: loading new config: http app module: start: listen udp :443: bind: address already in use
root@ifsmp-proxy:/home/ubuntu# 

How do I make the TLS certificate work but not interrupt the reverse_proxy on the same port?
Here’s my Caddyfile right now:

:443 {
        reverse_proxy 172.96.140.17:25697
}