Try adding a user to the container

Dockerfile

@@ -3,6 +3,10 @@ ARG MINECRAFT_VERSION="1.16.5"
 ARG FORGE_VERSION="36.2.26"
 ARG JRE_VERSION="openjdk8-jre"
 
+ARG UID=1520
+ARG GID=1520
+ARG USER=minecraft
+
 # The first stage just builds up the modpack
 FROM alpine:latest AS build
 
@@ -29,7 +33,9 @@ ARG JRE_VERSION
 
 # Build the thing up
 RUN apk add bash curl findutils rsync screen "${JRE_VERSION}"
+RUN groupadd -g $GID -o $USER && useradd -m -u $UID -g $GID -o -s /bin/bash $USER
 WORKDIR /minecraft
 COPY --from=build /minecraft .
+USER $USER
 CMD [ "bash", "start-server.sh" ]
 EXPOSE 25565