I’ve installed it using the source files. From the notes, the steps I’ve followed are:

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


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