Personally, I'm a fan of https://github.com/diafygi/acme-tiny. 200 lines of python without any additional python requirements and only the openssl binary as external dependency.
http://git.9front.org/plan9front/plan9front/HEAD/sys/src/cmd...
It works quite well, and if you mount your unix machines via sshfs, it's pretty easy to dump the certs into the right place with them.
And unlike most ACME clients, it works seamlessly with DNS authentication, which allows you to easily grab wildcard certs.
I maintain my own patch, so tiny-acme supports an '--outfile' option (it originally only writes to stdout). This comes in handy when it is run by systemd service/timer.
The pull request is on hold, because the code then exceeds then 200 lines threshold :shrug: