see https://cgit.freedesktop.org/upower/log/
Where are now the tarballs? I cannot find the 0.99.8 one https://upower.freedesktop.org/releases/
I found the tarball used in Fedora (and I also see other distros simply relied on it or plain git) [master 93dfe5ba210a] sys-power/upower: Version bump 2 files changed, 92 insertions(+) create mode 100644 sys-power/upower/upower-0.99.8.ebuild