Unfortunately, createrepo command which can create RPM repositories was removed in Ubuntu 20.04 LTS.
It's almost impossible to run package from Ubuntu 18.04 as plenty of dependencies were removed.
Let's try building C based version of createrepo from: https://github.com/rpm-software-management/createrepo_c
First of all, install all dependencies:
sudo apt install -y libcurl4-openssl-dev libbz2-dev libxml2-dev libssl-dev zlib1g-dev pkg-config libglib2.0-dev liblzma-dev libsqlite0-dev libsqlite3-dev librpm-dev libzstd-dev python3.9-dev cmake
Then build it:
mkdir createrepo_folder; cd createrepo_folder
git clone https://github.com/rpm-software-management/createrepo_c
cd createrepo_c;
mkdir build
cd build
cmake .. -DWITH_ZCHUNK=NO -DWITH_LIBMODULEMD=NO
make -j
cp src/createrepo_c /opt/createrepo
/opt/createrepo /var/public_repositories/Directory walk startedDirectory walk done - 18 packagesTemporary output repo path: /var/public_repositories/.repodata/Preparing sqlite DBsPool started (with 5 workers)Pool finished