Ask HN: S/MIME for email encryption in 2020/2021?

A recent frontpage HN article, which read more like a rant at the state of secure e-mail, made me think about what security options those of us have who choose to use common cloud e-mail providers. Considering the option of S/MIME, how would one get started using this signing and encryption method to exchange secure e-mail with associates? Is there any value in being the first to show an S/MIME signature and encourage others to jump on board? And what is the preferred vendor for getting an official S/MIME certificate at low cost or free? (Comodo's offering from past years seems to be gone.)