siril

build from source
dependencies here (missing from the list: libheif-dev)

**EDIT 03-oct 2023:

we now also need libgit2-dev

**EDIT 05-ago 2023:

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Meson and autotools

git clone --recurse-submodules https://gitlab.com/free-astro/siril.git

Meson

# adjust the prefix to wherever you want to install Siril

meson setup --prefix /usr/local --buildtype release _build  -Denable-libcurl=yes -DlibXISF=false
ninja -C _build
ninja -C _build install

update

git pull
git submodule update
ninja -C _build install

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autotools

git clone https://gitlab.com/free-astro/siril.git
(if that fails try git:// instead of https://)
cd siril
./autogen.sh
CFLAGS=-g ./configure

make 

To run siril either:

make install

siril installs to /usr/local

Or -better-  run from the build folder without installing:
~/siril/src/siril

EDIT: this is also now necessary as of 29 March. In the ~/siril folder:
remove ~/siril/subprojects/librtprocess then...
git submodule update --init