Currently the only way to install a recent version of SiriL on the RPi is building from source. It’s not completely evident, neither extremely difficult This are the steps I’ve followed (I think, that nothing is missing)
sudo apt install -y libgtk-3-dev libconfig-dev libfftw3-dev libexiv2-dev libopencv-dev libraw-dev libffms2-dev libheif-dev libcurl4-gnutls-dev gnuplot cmake libgsl-dev ninja-build libcurl4-openssl-dev sudo pip3 install meson==0.54.2 git clone https://gitlab.com/free-astro/siril.git cd siril git submodule sync --recursive git submodule update --init --recursive meson --buildtype release _build ninja -C _build sudo ninja -C _build install