wkhtmltopdf: QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to /tmp/runtime-root

I am using Docker image php:8.0-fpm-alpine3.14 which I have a Sylius project and I would like use wkhtmltopdf, so I added these lines in Dockerfile:

RUN apk --update --no-cache add \
   wkhtmltopdf \
    libgcc \
    libstdc++ \
    musl \
    qt5-qtbase \
    qt5-qtbase-x11 \
    qt5-qtsvg \
    qt5-qtwebkit \
    ttf-freefont \
    ttf-dejavu \
    ttf-droid \
    ttf-liberation \
    xvfb \
    fontconfig

# Add openssl dependencies for wkhtmltopdf
RUN echo 'https://dl-cdn.alpinelinux.org/alpine/v3.8/main' >> /etc/apk/repositories && \
    apk add --no-cache libcrypto1.0 libssl1.0

RUN ln -s /usr/bin/wkhtmltopdf /usr/local/bin/wkhtmltopdf;
RUN chmod +x /usr/local/bin/wkhtmltopdf;

But I get this error when I try to use wkhtmltopdf:

I don't understand why I get that error et how to fix that.

Thank you