@AndreKR messaged me with a solution that may be helpful:
This thread ends without the actual solution. Symfony needs REQUEST_URI to be correct and inside a handle_path it is arguably wrong. I eventually found the actual solution in Caddy 2.6.2 handling of strip_prefix is broken · Issue #5312 · caddyserver/caddy · GitHub
Since the thread is closed, I’m adding it to the thread for others who may be searching 